US 5,732,270 AGrant
System and Method for Providing Interoperability Among Heterogeneous Object Systems
Issue Date:1998-03-24
•98 Claims
•17 Drawing Sheets
Abstract
A system and method in accordance with a preferred embodiment enable objects from two or more heterogeneous object systems in a digital computer to interoperate and be combined in the creation of a larger object-oriented software project, as well as uses of such system and method. Objects from a foreign object system are unmodified, yet appear to be native to the object system in which they are used or accessed. A native proxy object (indistinguishable from other native objects) is constructed for the real foreign object. The proxy object contains an identifier to the real object, as well as a pointer to a software description of how to access and manipulate the object--e.g. how to call its methods, set its properties, and handle exceptions. When the proxy object is manipulated, it follows the instructions in the software description which, in turn, results in the corresponding manipulation of the foreign object.
Metadata
Assignee
- Visual Edge Software Limited
Inventors
- Daniel M. Foody
- Michael A. Foody
Application Information
Application Number:US 3064816
Filing Date:1994-09-15
Priority Date:1994-09-15
Art Unit:236
Classifications
IPC:
G06F 944
Field of Search:
395700;683;200.01
Patent Drawings (17 sheets)
Description
Technical Field
The present invention relates to object-oriented software systems and related methods for digital computers.
Background Art
Using object-oriented software techniques, software applications for digital computers are created by combining software objects. To facilitate this process, object-oriented software systems typically provide an architecture specification, called the object model, which enables all objects developed to the specification to work together seamlessly in an application. Examples of object models would include the Object Management Group's Common Object Request Broker Architecture (CORBA), and Microsoft's Common Object Model (COM.) Such systems also typically provide software, called the object system, which implements the basic features provided for in the object model.
There are numerous object systems, some very general in nature such as Microsoft's Object Linking and Embedding (OLE) (which follows the COM object model), or IBM's Distributed System Object Model (DSOM), and Iona's ORBIX, (which both follow the CORBA object model). See for example: the OLE 2 Programmers Reference, Volume 1 and 2, Microsoft Press, 1994; the IBM SOMobjects Developer Toolkit V2.0, Programmers Reference Manual, 1993; Iona ORBIX, Advanced Programers Guide, 1994; and The Common Object Request Broker: Architecture and Specification Ch. 6., OMG, 1991; these references are hereby incorporated herein by reference.
Other object systems are designed to provide specific functionality, for example, in areas such as groupware or relational database--e.g. Lotus Notes. Still other object systems are specific to particular to applications--e.g. Novell's AppWare Bus, Hewlett Packard's Broadcast Message Server, and Microsoft Visual Basic's V'BX object mechanism. See for example: the Lotus Notes Programmers Reference Manual, 1993; the Novell Visual AppBuilder Programmers Reference Manual, 1994; the Hewlett Packard Softbench BMS, Programmers Reference Manual, 1992; and Microsoft Visual Basic 3.0 Professional Features Book 1, Control Development Guide, 1993; these references are also hereby incorporated herein by reference.
In creating a software application it is desirable to combine objects from various object systems, because different object systems are best suited to different tasks, and because the best solution is usually built from the best parts (i.e. objects.) However, objects from various object systems don't naturally work together for a number of reasons.
Object systems are rendered incompatible due to differences in the means by which objects are created, methods are called and properties are set in each object system, including differences in the fundamental mechanisms used as well differences in low-level calling conventions such as the physical layout of types and classes. For example at the fundamental level, some object systems, such as COM, use direct C++ calling mechanisms. Others such as DSOM pre-process source code so that in place of a direct call, a function from the object system is called which, in turn, returns a pointer to the real method. This pointer is dereferenced to actually call the method. Still other object systems such as OLE Automation provide specialized functions developers must use to call methods (this is often referred to as a Dynamic invocation Interface or DII). These functions take the method to be called as an argument, as well as the method's arguments (usually packed into a particular format), and they call the method for the developer. There are numerous other broad differences and variants in fundamental calling mechanisms. Each of these fundamental mechanisms also differ in detail. For example, CORBA requires an environment pointer argument (and has an optional context argument), while other object systems do not.
In addition to the vast differences in fundamental calling mechanisms, there are many differences in low-level calling conventions, sometimes referred to as procedure calling conventions. For example, different object systems handle the return value from methods differently when the type of the return value is a float or a structure. In one case the value may be returned on the processor stack, while in another the value may be placed in a register. Thus, using the return value of a method from a different object system would result in an error. Other examples of differences in procedure calling conventions would include how structures are packed into memory, and how arguments are placed on the stack.
Various object systems also support various types which may not be compatible with other object systems. Simple examples of types include language types such as integers, floats, etc. More complex language types include arrays, strings, and objects. There are also semantic types such as "variable types" like the CORBA Any, and the COM VARIANT. Semantic types differ from language types in that they have a particular semantic meaning to the system. While certain semantic types may conceptually mean the same thing among various object systems, their corresponding language representation and implementation may be entirely different. A common example is strings. In COM, strings are represented using a "BSTR" (a non-NULL terminated string which contains length information), while in CORBA, strings are the traditional C language byte array (NULL terminated with no length information). As a result, a COM object couldn't pass a BSTR to a CORBA object because any functions that operate on strings, such as copying and comparison, used in the CORBA object would fail. Likewise, while "variable types" such as the CORBA Any and the COM VARIANT "mean" the same thing, they aren't compatible.
In addition, object systems have various rules about lifecycle management which may be incompatible. The term lifecycle management refers to the process required when creating, storing, and deleting objects. For example, COM requires developers to perform reference counting so objects can be automatically deleted. Relational databases have much more sophisticated lifecycle management, while CORBA has only very simple lifecycle management with no reference counting.
The above issue of lifecycle management is challenging because often, objects are passed as arguments to methods. Consider the case where an object in one object system calls a method of an object in a foreign object system and passes an object (from its object system) in as an argument to the method. Since the foreign object system only understands its own objects, the object argument must be dynamically converted to a corresponding object in the foreign object system. In other words, a new object must be created in the foreign object system to match the original object passed in as an argument. All such dynamic lifecycle management--object creation, with its corresponding object destruction--must be handled properly if object system interoperability is to work.
Another aspect of object system interoperability is differences in exception and error handling among object systems. Errors or exceptions encountered within the code for an object typically must also be dealt with in the object which called the code. If the two objects are from different object systems, and the error handling mechanisms are incompatible, software failure may result.
Various object systems provide different ways to dynamically query for information about objects. This functionality is required for object systems that provide a general macro script recording facility as well as for object systems that provide distributed computing capabilities. See for example Ch. 1-3 of Microsoft's OLE 2 Programmers Reference Volume 2, Apple's Inside Macintosh: Interapplication Communication Ch. 8 (hereby incorporated herein by reference), or the Object Management Group's The Common Object Request Broker: Architecture and Specification Ch. 6. Thus, incompatibilities in the mechanisms to query for information about objects results in significant restrictions in the ways that objects may be used in other object systems.
As mentioned previously, object systems each have different design goals. As a result, each typically has functionality that isn't available in other object systems. Two examples of this are: CORBA namespaces (which COM doesn't have); and COM objects supporting multiple interfaces (which CORBA doesn't have). Software errors can result if an object is asked to perform some action that is only available in another object system.
In summary then, a sought after goal has been to provide interoperability among various object systems. Different object systems place different requirements on objects, so specialized software systems are required to enable interoperability. The prior art includes approaches to providing interoperability between object systems. Three solutions are of interest: stub function wrappers; a common wire protocol; and dynamic converters.
With the stub function wrapper method, an automated tool is used to generate stub functions which "wrap" objects in code that follows the specification of another object model. That is, the tool creates an object class in the foreign object system that contains only the code necessary to forward requests to the native object. This "stub" code is then compiled and linked into an application. The stub function method is exemplified by the COM interoperability provided with IBM's DSOM for Windows. Using it, developers who have DSOM objects and want to use them from within COM use an automatic tool to generate source code for corresponding COM objects. The source code for the COM objects is simply a set of stub functions which forward calls to DSOM. For example, when the COM application calls a method of the COM object, the method simply re-calls the DSOM version of the method.
One automated tool to create a set of stub function wrappers provides one-way interoperability between two object systems. To provide two-way interoperability--as is required for dynamic lifecycle management, a second tool has to be written. If an additional object system is to be supported, and full interoperability among all three systems is required, an additional four automated tools must be written. In fact, the number of such tools required for interoperability among N object systems is N.sup.2 -N In addition, for each object class, N.sup.2 -N versions of stub wrapper functions must be generated, managed and supported. Given that any particular application will have hundreds of classes, this is a significant disadvantage. Furthermore, this method provides no support for the remainder of interoperability issues such as dealing with type conversions, low level calling convention differences, lifecycle management differences, differences in error and exception handling, querying, or functionality differences. As a result, users of the object must code such conversions into their software manually, making it apparent that the object is from another object system (i.e. the object is clearly not indistinguishable from native object.) Finally, support for new object systems is not dynamic, so code must be recompiled and relinked.
Dynamic converters are designed to provide interoperability between two object systems that both support a dynamic invocation interface (DII). A DII "dynamically invokes" methods. That is, a DII is a set of functions that will call an object's methods for the developer dynamically, and pass arguments to the methods using a pre-defined convention, rather than requiring that the call be compiled into the application. A dynamic converter is a hard-coded map between two DIIs. When a method is called, the converter code packages the information into a format suitable for the DII of the second object system, then calls the method.
As with the stub wrapper mechanism, this approach requires N.sup.2 -N converters in order to support N object systems. Furthermore, dynamic converters only work with object systems that support a DII. Moreover because they use a DII their performance suffers. And, as with the stub wrapper method, this method provides no general support for the remainder of interoperability issues such as dealing with type conversions, differences in error and exception handling, querying, or functionality differences--thereby being unable to provide foreign objects which are indistinguishable from native objects.
The common wire protocol method is designed to work with distributed object systems, that is, object systems whose objects may be located on different computers having different machine architectures. With the common wire protocol method, object systems which share a common underlying distributed computing system (DCS)--the "common wire" --can interoperate The common distributed computing system enables object systems to transfer language data types, because a non N.sup.2 -N language data type transfer mechanism is provided by the DCS.
This approach addresses the issue of low level calling conventions and provides mapping of low level data types. The complexity of supporting N object systems depends directly upon whether the object systems share the same object model. If so, there is no need to provide interoperability between fundamental calling convention differences, semantic type differences, lifecycle management differences, differences in error and exception handling, or functionality differences, and each object system requires only to support the DCS. This case would be exemplified by interoperability among various CORBA object systems such as IBM's DSOM, Iona's Orbix, Hewlett Packard's DOMF, etc. which can each use the Open Software Foundation's Distributed Computing Environment (DCE).
If interoperability is among object systems that don't share a common object model, the approach requires N.sup.2 -N converters to deal with the remaining issues. Furthermore, this method doesn't work at all if the object systems which must interoperate are not built on top of a shared distributed computing system. And the approach is very resource intensive due to the reliance on a DCS. While it handles transfer of simple data types, it provides no general mechanism to handle more complex type conversions, lifecycle management differences, differences in error and exception handling, querying, or functionality differences--resulting in similar deficiencies to other prior art.
Along with the above prior art directly addressing the issue of object system interoperability, there is other prior art addressing various elements of the problem, each in a different context.
There have been a number of systems that have dealt with the issue of mapping between different low-level calling conventions. In U.S. Pat. No. 4,736,321, a method was described wherein an interactive language workspace, APL, was able to call external language procedures. In it, FORTRAN functions were declared to the APL environment, and the APL environment mapped the APL calls and arguments into FORTRAN calling conventions. The method in this patent is specific to the interactive APL language environment and provides unidirectional access from APL to multiple languages (FORTRAN and Assembler). The method doesn't support bi-directional access among any number of languages, and doesn't work among compiled language code systems.
A similar mechanism was described for Prolog in U.S. Pat. No. 5,274,821 wherein a Prolog language procedure could call external language functions and vice versa. In this patent, the mapping was accomplished using a table driven approach. That is, mapping of Prolog to multiple languages, and mapping multiple languages to Prolog was accomplished by describing the low level calling convention to the system in a table. This information was used at execution time to dynamically perform the mapping. As with the method in U.S. Pat. No. 4,736,321, this method is specific to an interactive language environment, in this case, Prolog. It provides bi-directional mapping from Prolog to N languages, but not among N languages. The method doesn't work among compiled language code systems, and in any case would require N.sup.2 -N conversion tables.
A mechanism was described in U.S. Pat. No. 5,210,876 wherein an interpreter is able to call a compiled procedure, which in turn, calls an interpreted procedure. The means was to generate a new intermediate compiled procedure which is called by the original compiled procedure. The new compiled procedure was then dynamically linked with the original compiled procedure. The new generated procedure converted arguments to the format required by the interpreter, then called the interpreted procedure. Finally, the results were converted back to those required by the compiled language. As with other prior art, this patent facilitates an interpreted environment calling compiled language code. And as with other prior art, N.sup.2 -N code generators would be required to support procedure calling convention conversion among N systems.
U.S. Pat. No. 5,097,533 describes a method for interfacing various pre-determined computer languages to a single software system. In it, code is written for each language to map from the API in the language to a single API for the underlying software system. This patent maps procedure calling conventions from N languages to one by writing code to perform the mapping for each. The method does not work for conversion among N language conventions, and in any case would require N.sup.2 -N code blocks to be written.
In U.S. Pat. No. 5,146,593, a method is described wherein a single software interface is used to call a plurality of procedures. In fact, this is but one example of a DII--a DII designed for mapping to different programming languages. In it, the method uses tables to describe the low level calling conventions of the particular language. The user (i.e. the software developer wishing to make the calls) links the DII interface with their application and uses it to make all their calls by passing it a procedure identifier, and data structures in a predefined format. The method doesn't support interoperability among N language calling conventions, and would also require N.sup.2 -N tables should the approach attempt to be extended for that purpose.
The above patents share the fact that they are designed to provide a mechanism to deal with the differences between low-level calling conventions of various languages. With the exception of U.S. Pat. No. 5,210,876 they each provide a means of converting various language types as well. However, they don't address the issue of differences between high level calling conventions. In fact, they each a provide a different high level calling convention, so they have no need to. Nor do they provide any support for mapping between semantic types.
Other patents, for example U.S. Pat. No. 5,187,787 have dealt with the issue of mapping between semantic types. In this patent, mapping between semantic types was but one element of a larger system used to provide a communications interface which decoupled two software applications. In it, the semantic types used in the communication were designed by to be self-describing. The patent teaches that the semantic description must be separated from the data representation for interoperability. Further, developers use a system API to access data, which may be located elsewhere, and in another semantic form. Thus, the mechanism requires explicit knowledge on the part of the developer to use the decoupled data, and is analogous to a single DII, with the same consequent limitations.
In U.S. Pat. No. 5,278,978, a method was described to transfer information between two databases. As a part of the system, a mechanism was described to map between both language types and semantic types. Each language type was tagged with a canonical identifier called a marker descriptor. Likewise, separately, each semantic type was tagged with a canonical identifier called a type definition. When data was received from another database, the descriptions were used to perform a conversion. Each database was required to have predefined descriptions of all other machine environments and semantic types, i.e. N.sup.2 -N conversion descriptions, because conversion was performed at the receiving database.
Summary of the Invention
This invention provides in some embodiments a single system in a digital computer enabling software objects from multiple heterogeneous object systems to interoperate bidirectionally and to be combined in the creation of a larger software system. Objects from a foreign object system are unmodified, yet appear to be native to the object system in which they are used or accessed. Support for additional object systems may be added dynamically while the system is executing, thereby adding bi-directional interoperability with all other supported object systems. A mechanism is also provided whereby features in one object system may be supported in other object systems without the necessity of modifying objects.
For a foreign object to be used in another object system, the system of these embodiments constructs a native proxy object (indistinguishable from other native objects) for the real foreign object. The proxy object contains an identifier to the real object, as well as a pointer to a software description of how to access and manipulate the object--e.g. how to call its methods, set its properties, and handle exceptions. When the proxy object is manipulated, it follows the instructions in the software description which, in turn, results in the corresponding manipulation of the foreign object.
The system of these embodiments provides a number of object-oriented frameworks with default implementations. There are frameworks to: dynamically locate objects in an object system-specific or uniform namespace; describe the characteristics of an object class or instance; describe both semantic and language types; "execute" the software descriptions to forward manipulations of the proxy object to the real foreign object; handle errors and exceptions; create, copy, destroy, and manage the lifecycle of objects; and a framework to "export" object definitions--i.e. to make objects in one object system appear as object classes indistinguishable from native object classes temporarily or permanently in other object systems.
In addition, there is a framework to add extra information to the description of any object class. Such added information is called a "mixin". When an object is manipulated in a way it doesn't support, for example if it is asked to return the middle element of a collection but it doesn't support such a method, the system asks the mixins associated with the object if they can support the request. If so, they take over and perform the request. In this way, a general mechanism is provided to extend the capabilities of objects in an object system with features of other object systems that they wouldn't naturally support.
Extensions to the default implementations of each of the above frameworks are grouped by object system, and packaged into libraries called Object System Adapters (OSAs). OSAs can be dynamically loaded into the OSA Registry framework of the system, thus adding everything necessary to dynamically support new object systems and provide full interoperability with other object systems.
It will be obvious to those skilled in the art that the system may be used stand-alone, or embedded as an element of a larger software system.
Further embodiments of the invention are also provided:
(A) a system and method to enable the creation of a "universal object", i.e. a single object which appears to be implemented in a plurality of object systems simultaneously, and which can dynamically change which object systems it supports. Said system also enables the creation of objects in individual, application, and server configurations. Further, such objects may be based upon interpreted or compiled language technology;
(B) a system and method--either library-based or interactive--to enable the construction of object classes including the aforementioned "universal object", where such system in the creation of said object classes, may constitute a subclass of, incorporate, or embed instances of, objects from a plurality of object systems;
(C) a system and method to enable object classes and objects to be relocated among applications and servers in one or more object systems while the applications and servers are executing, and without disruption of software utilizing said object classes and objects, even if it too is executing.
Brief Description of the Drawings
The foregoing aspects of the invention may be more readily understood by reference to the following detailed description, furnished in connection with the following drawings, in which:
FIG. 1 is a simplified overview of a system (in use) in accordance with a preferred embodiment of the invention;
FIGS. 2, 2b are an overview of the system architecture in accordance with a preferred embodiment of the invention;
FIG. 3 shows Object System Adapters of FIG. 2 plugged into the Adapter Registry Framework;
FIG. 4 shows the description of a class with one method and one property in accordance with the embodiments of FIG. 2;
FIG. 5 shows a nested type description in accordance with and one property in accordance with the embodiment of FIG. the embodiment of FIG. 2;
FIG. 6a, 6b show the description of a method which follows the CORBA C language calling convention;
FIGS. 7a, 7b, 7c show the description of a similar method which is called using a Dynamic Invocation Interface;
FIG. 8 shows the typical lifecycle of an object;
FIG. 9 shows the process used to expose classes using the system of FIG. 2;
FIG. 10 shows a typical proxy object in accordance with the embodiment of FIG. 2;
FIG. 11 shows a configuration of the invention in which an object appears to be implemented in a number of object systems and processes simultaneously;
FIG. 12a, FIG. 12b, and FIG. 12c, respectively, show individual, application, and server configurations of "universal objects" in a accordance with a preferred embodiment of the invention;
FIG. 13 shows a class hierarchy of a class registry according to the present invention;
FIG. 14 shows a sample instance hierarchy according to the present invention; and
FIG. 15 shows a table summarizing which usage codes apply to which classes and also which users are most likely to refer to a usage code.
Detailed Description of Specific Embodiments
FIG. 1 shows a simplified overview of the system 105 in use in a digital computer in accordance with a preferred embodiment of the invention. Process 101 is implemented using a first object system, referred to as the "native" object system, distinct from a second object system in which process 102, and object 103 are implemented. The second object system, implementing process 102 and object 103, is referred to as the "foreign" object system (foreign relative to the process 101 which is using the object 103). The system 105 has constructed a proxy object 100. The proxy object 100 appears indistinguishable from other objects implemented using the native object system in process 101. The proxy object 100 established by system 105 contains a pointer to the real object 103, as well as to a software description 104, of how to access and manipulate the real object 103--e.g. how to call its methods, set its properties, and handle exceptions. When process 101 manipulates proxy object 100, the manipulations are intercepted by the system and forwarded to the real object 103. The system forwards the manipulation by following the instructions in the software description 104, which, in turn, results in the corresponding manipulation of the real object 103. The system can follow the instructions in the software description 104 regardless of which object system created it, thus resulting in a non-N.sup.2 -N approach to object system interoperability.
Referring to FIG. 2, there is shown a simplified architecture diagram of the system in accordance with a preferred embodiment of the invention. As described below, applicants have successfully implemented this embodiment on a wide range of hardware platforms in a wide range of object systems. In the diagram, the triangular symbol 110 indicates that items to its right are subclasses. The system includes nine frameworks as follows:
the Location and Enumeration Framework 1 to dynamically locate objects in an object system-specific or uniform namespace. Included in this framework is the ability to determine the characteristics of objects that have been located;
the Class Description Framework 2 to provide a description of the characteristics of an object class or instance;
the Type Description Framework 3 to provide a description of and to convert both semantic and language types;
the Forwarding Engine Framework 4 to "execute" the software descriptions to forward manipulations of the proxy object to the real foreign object;
the Error and Exception Handling Framework 5 to handle errors and exceptions;
the Lifecycle Management Framework 6 to create, copy, destroy, and manage the lifecycle of objects; and
the Object Exporting Framework 7 to "export" object definitions--i.e. to make objects in one object system appear as object classes indistinguishable from native object classes temporarily or permanently in other object systems.
In addition, there is the Mixin Support Framework 8 to add extra information to the description of any object class, enabling the support in all object systems of features found only in one object system. There is also the OSA Registry Framework 9 to load, unload, and manage Object System Adapters (OSAs) 10. The OSAs 10 are libraries that package together extensions to the default implementation of each aforementioned framework provided by the system. When added, they provide full bi-directional interoperability among all other object systems with corresponding OSAs loaded.
A more detailed description of the above architecture may be found at the end of the present specification. It will be understood by those skilled in the art that this architecture may be reorganized without affecting the utility of the embodiment described.
FIG. 3 shows the OSA Registry framework 9 as well as a number of OSAs loaded. In this configuration, the system provides interoperability among the four object systems corresponding to the OSAs.
A specific embodiment of the invention has been written in C++ and runs on Microsoft Windows 3.1 and Windows NT, IBM OS/2 and AIX, Sun Microsystems SunOS and Solaris, as well as on Hewlett Packard HP-UX. Object System Adapters have been implemented for Microsoft OLE Automation, IBM SOM and DSOM, Microsoft COM, and for the Microsoft Visual Basic VBX object system. In addition, an OSA has been implemented for an interpretive language environment. The embodiment currently provides support for enabling objects implemented in pure C++ to be used in object systems with corresponding OSAs. Likewise, the embodiment currently provides support for enabling software written in C (i.e. not written to any object system) to be used in object systems with corresponding OSAs.
The sections below describe each of the above frameworks, and the section numbers below correspond to the item numbers in FIG. 2.
1) The Location and Enumeration Framework: a framework to dynamically locate objects in an object system-specific or uniform namespace.
The Location and Enumeration framework has two primary sub-frameworks as shown in FIG. 2b, an object system-specific namespace sub-framework called an "Adapter NameSpace" 111, and an object system-independent namespace sub-framework called a "View NameSpace" 112. Together, adding support in the framework for new object systems requires only that the Adapter NameSpace be subclassed--a linear (i.e. non N.sup.2 -N) operation.
The Location and Enumeration Framework provides a suite of generic capabilities which may be used by OSAs or overridden (in the object-oriented sense) and replaced with capabilities specific to an individual object system. More specifically, the Adapter NameSpace 111 provides searching capabilities to locate a particular, or a complete list of: classes, instances, functions, types, exceptions, sub-namespaces, or any combination therein in the object system. It will be apparent to those skilled in the art that numerous well known search techniques, such as regular expression matching, may be applied during the search process. Using object-oriented principles, a single interface--the Adapter NameSpace interface--is therefore utilized by the remainder of the system to search any particular object system to determine and return the hierarchy of information it provides.
Items in Adapter NameSpaces may be enumerated upon execution of the system or loading of the particular OSA. More often, however, Adapter NameSpaces will not enumerate their contents until required, as would be the case if a user performed a browsing operation, if the system had to construct an object of a particular class, or if the system had to make a class visible in another object system.
Adapter NameSpaces enumerate their contents using generic mechanisms provided by the system, or by supplying object-specific mechanisms. Generic mechanisms provided by the system include static mechanisms, dynamic mechanisms, or database mechanisms. With static mechanisms, users of the system call system APIs to register their information. With dynamic mechanisms, the system queries the objects themselves (or the software utilizing the system, such as a language interpreter's symbol table) to determine the information. With database mechanisms, the system reads a file, or a repository to determine the information. Examples of the latter would include querying information from a CORBA interface repository, reading a COM Type Library, reading "header files" (e.g. C++ header files or CORBA IDL files), or reading the symbol table of a "dynamic link library". Typically, each OSA would have to override some capabilities of the generic mechanisms.
The second sub-framework, View NameSpaces 112, provides an object system independent mechanism to organize information such as classes, instances, types, etc. View NameSpaces, may be organized in a acyclic graph. View NameSpaces may also be subclassed to provide particular capabilities such as a flat list of named objects (i.e. classes, instances, types, etc.). Any item enumerated in an Adapter NameSpace may be placed in a View NameSpace, including then entire NameSpace of an OSA. As is typical of file systems, aliases are provided, and circularities are recognized. In this way, users of the system have a means to fully locate and organize information in an object system independent way.
2) The Class Description Framework: a framework to describe the characteristics of an object class or instance.
Contained in Adapter and View NameSpaces is the information to describe classes. The Class Description Framework is provided to enable this capability, and to enable OSAs to override built-in functionality. The Class Description Framework consists of a suite of classes which describe: classes, instances, properties, functions (including methods), arguments, and exceptions. The corresponding classes used are entitled, respectively: VClassData, VinstanceData, VPropData, VFunctionData, VArgumentData, and VExceptionData. An additional framework to describe types, the Type Description Framework as described below, is also utilized. Each of the above classes can be asked for the name of the object it represents, its type, its owner (e.g. if it describes a class property, its owner would be the class), the object system that manages it, as well as "usage codes" (described below).
The class in the Class Description Framework which is used to describe classes (as opposed to describing properties or methods) is called VClassData. VClassData provides descriptions of the class it represents to the rest of the system by returning results from method calls rather than by building a static data structure, a linked list data structure, or the like. For example, it provides a class method which returns a list of properties. This enables OSAs to subclass VClassData and override its methods in order to provide the class description using an object system-specific implementation, while still providing a single API to the rest of the system.
The VClassData class has methods to return, for the class it describes: the base classes (as a list of VClassData); the constructor, duplicator, and destructor (as VFunctionData); the class' methods (as a list of VFunctionData); the class' properties (as a list of VPropData); the class' exceptions (as a list of VExceptionData); as well as a method to return a named instance of the class.
The class in the Class Description Framework which describes functions and class methods is called VFunctionData. The VFunctionData class has methods to return, for the function it describes: the arguments (as a list of VArgData), the exceptions the function can throw (as a list of VExceptionData), and a callable entry point for the function (or method).
The class in the Class Description Framework which describes class properties is called VPropData. The VPropData class has methods to return, for the property it describes: a method to set the property, as well as a method to get the property (both as VFunctionData).
Likewise, the class in the Class Description Framework which describes function arguments, VArgData, has methods to return the name, the type, and the usage codes for the argument it describes. The class which refers too instances, VinstanceData, has methods get and set its value (i.e. the actual instance). The class which describes exceptions is described below in the section on error and exception handling.
The above information is typically constructed by the OSA as NameSpaces are enumerated, however, it may be constructed directly by the user of the system. If the OSA doesn't override any capabilities, as it enumerates its contents, it would typically use subclasses of each of the above classes which, in addition to having methods to retrieve information, have corresponding methods to set the information. Thus, as the OSA determined the contents of the object system, it would construct the necessary instances of the above classes, and call their methods to "connect" them. For example, it would construct the subclass of VClassData which supported these methods, then construct VPropData corresponding to the class' properties, then call a method to set the list of properties in the (subclass of) VClassData. FIG. 4 shows the results of an OSA constructing the description of a DSOM class 11 with one method 12, and one property 13. The method takes one argument 14 and 15, a short, and returns a long 16. The property 13 is of type short 17, has a function to set its value 18 that takes a short argument 19 and 20, and returns a void 21. The property also has a function to get its value 22 that returns a short 23. It will be apparent to those skilled in the art, that the information need not be organized in a tree as shown in FIG. 4.
3) The Type Description Framework: a type management framework to describe both semantic and language types.
Analogous to the Class Description Framework is the Type Description Framework to describe types, including both semantic and language types. The Type Description Framework provides a base class for describing types called VTypeData, as well as a subclass of VTypeData called VcrFundamental for representing fundamental types such as integer, float, double, byte, unsigned long, etc. In addition, complex types such as structures (VcrStruct), unions (VcrUnion), pointers (VcrPointer) and function pointers (VcrFunctionPointer), object references (VcrObjectRef), sequences (VcrSequence) including arrays (VcrArray) and strings (VcrString), enums (VcrEnum) and the like can be described using these subclasses of VTypeData. Types can also be nested to create arbitrarily complex types. FIG. 5 Shows the description of a type which is a pointer 24 to a structure 25 containing two items 26 and 27. The first item is a short 28, while the second item is a long 29.
4) The Forwarding Engine Framework: how do these descriptions make it possible to forward manipulations of the proxy object to the real foreign object?
The above elements, class and type descriptions, are combined to fully describe a class. Two key aspect of the method are that elements are tagged as to whether they are semantically meaningful or not, and both semantic and nonsemantic information are contained in the description. As a result, the description method is capable of fully describing the fundamental calling mechanism, as well as the language calling convention. For example, FIG. 6a shows a declaration for a simple method call following a CORBA calling convention. The method 35 takes four arguments: the object 30, the Environment pointer 31 (a characteristic of all CORBA method calls, the Environment pointer is most commonly used as the mechanism to return errors), as well as arguments entitled X 32, and Y 33. The method returns void 34. FIG. 6b shows the corresponding description of this method.
FIG. 7a shows the same method in a different object system which uses a different calling convention. In this declaration, a Dynamic Invocation Interface (DII) 41 is used to call the method. The first argument 36, is the object. The second argument is an identifier for the method 37. Next is a count of the number of arguments 38. Finally, the arguments are packed into an array 39. The DII returns an error pointer 40. FIG. 7b shows the corresponding description of this call. Notice that in both cases, only the object, X, and Y are tagged as being semantically meaningful (SM). The other described aspects are merely artifacts of how to make the method call.
In summary, to forward method calls from one object system to another, the forwarding engine walks down the description of the method call that was made, and pulls all semantically meaningful information from the calling stack. It then walks down the description of the method call it is about to make, and puts all the described information on the "call stack" (each computer system processor has particular rules about where to place arguments prior to making a function call, such place generically referred to as the "call stack"), transferring the semantically meaningful information to the correct position (and converting types if necessary.) It then calls the correct function to actually invoke the method. Once the method has returned, it likewise transfers the results back to the original method call stack.
Shown in FIG. 7c are the steps that might take place if an object implemented in the object system of FIG. 7, hereafter referred to as the foreign object system, was being used by software written in the object system of FIG. 6, hereafter referred to as the native object system, when the method 35 of FIG. 6 was called.
First, based on the way the OSA constructed the proxy, the OSA receives the flow of control 701 from the software which manipulated the proxy. Next, based on the layout of the proxy it has constructed, the OSA of the native object system retrieves the real object, as well as the VFunctionDatas for both the real object and the proxy object 702. These are passed to the Forwarding Engine Framework. The layout of a typical proxy object is shown in FIG. 10 and described in section 7) below the layout of
The first major step the Forwarding Engine Framework performs is to traverse the VFunctionData of the proxy, using it to retrieve all semantically meaningful information from the just-occurred method call 703. It asks the for its list of arguments (i.e. the list of VcrArgument). For each argument determines if the argument is semantically meaningful. If the argument itself is not semantically meaningful, yet the argument is a complex type, the argument may still within itself contain semantically meaningful information. Thus, the Engine must traverse the contents of the argument recursively to ensure that no semantically meaningful information is within it.
Information which is not semantically meaningful is discarded, while semantically meaningful information is stored. In this example, the first argument 30 is the object upon which the method was called. It is semantically meaningful, therefore it is stored (although for optimization it need not be, since this identifier to the proxy object has already been retrieved by the native OSA).
The next argument 31 isn't semantically meaningful, so it is ignored. The third and fourth arguments, 32 and 33 respectively, are semantically meaningful, and so are retrieved and stored. See, for example, the Intel486 Microprocessor Family Programmer's Reference Manual 1992, hereby and hereinafter incorporated by reference, for an in depth explanation of how to retrieve information from a function call made on the Intel 486 microprocessor.
Having retrieved all semantically meaningful information from the original method call, the next major step taken by the Forwarding Engine is to begin constructing the method call for the real object by placing the appropriate arguments on the "call stack" 704. In this example, the Forwarding Engine would traverse the VFunctionData shown in FIG. 7 representing how to call the foreign object's (i.e. the real object's) method, retrieving the list of arguments.
The first argument 36 is semantically meaningful and must be placed on the call stack. The Forwarding Engine traverses the list of information retrieved from the original method call to find the matching information. In this case, the object. The object from the original call must be converted to the type required by the foreign call and placed on the stack. The Forwarding Engine contains an optimization which ascertains if the object required is the real object (which it is in this case) and so places the real object on the call stack. The second argument 37 is a string constant, "MethodName" (i.e. the name of the real method) which the Forwarding Engine places on the call stack. Likewise, the third argument 38 is the constant short whose value is 2, so 2 is placed on the call stack.
The fourth argument, 39 is a complex type, so the Forwarding Engine traverses its elements. The Forwarding Engine creates an array capable of containing two long integers. Then, it matches the first entry with the information retrieved from the original call, and so places X in the first position (as a long integer, no type conversion required). It performs the same for the second argument, Y. Once this is completed, it places the array on the call stack.
The third major step performed by the Forwarding Engine Framework is to call the actual method 705. The Forwarding Engine asks the VFunctionData 41 for the address of the function to call. In this example, it returns the address of the DII function. The Forwarding Engine then dereferences the pointer to actually call the function.
The next step performed by the Forwarding Engine is to handle the return values 706. The Forwarding Engine retrieves it from the call stack. The VFunctionData of the original method call is asked for its return type. The original method call returns void, so no information needs to be placed on the "return stack" (the term "return stack" refers generically to the computer processor-specific location or locations where the results of a function call are placed).
The final step before returning from the original method call is to handle errors and exceptions. In this example, the foreign method returns a pointer to error information 707. The original traversal of the VFunctionData identified the environment pointer as containing error information (the environment pointer is the native object system's standard mechanism to transfer error information). The Error and Exception Handling Framework is delegated the task of determining if an exception occurred, and converting the information from the form provided by the method call on the real object in the foreign object system to the form appropriate for the native object system. In this example, the necessary conversion takes place, control is returned to the forwarding engine, and ultimately to the process which originally called method 35.
Note that the series of steps taken by the Forwarding Engine can be automatically generated as source code and compiled for performance, if desired. Likewise, note that the above description was given in the context of method calls, however it applies to all manipulations. Furthermore, the object being manipulated need not be from an object system, as long as the requisite description is provided. For example, this enables straight C language software to appear to be implemented in any object system.
OSAs have a choice as to whether they have the system's Forwarding Engine Framework code handle forwarding of methods automatically, or whether they subclass the framework to provide a custom forwarding scheme. In some cases, the OSA can look at the description of the method call that is about to be made (i.e. not the one just made that has to be forwarded), and determine what semantic information must be removed from the call stack. By virtue of the fact that the OSA corresponds to the object system in which the call was just made, the OSA writer can code into the OSA how to remove information from the call stack--the OSA need not walk down a general description of its own method.
Likewise, the OSA that constructed the VFunctionData for the real method (i.e. the method in the foreign object system) can construct it so as utilize whatever means it finds necessary to accomplish the real call. For example, the OSA can construct the VFunctionData so as to "call back" into the OSA for further custom processing.
The above descriptions of classes aren't specific to any particular object system. They can be created by any object system to describe their classes, and they can be traversed and "executed" by any OSA to forward manipulations of objects by any object system to any other object system. As a result, the method to forward object manipulations isn't an N.sup.2 -N approach.
A similar method is used when objects are queried for a description of themselves. The description of the native object is traversed, as triggered by the proxy, either by the Forwarding Engine or by the OSA, and the semantic information converted to the format required by the object system making the request. The formatting of such information is one of the responsibilities of an OSA.
As mentioned, types, including semantic types such as strings and variables containing any type, as well as language types must often be converted between object systems. The system provides an object oriented type system, the Type Description Framework, capable of converting semantic and language types between any two object systems in a non-N.sup.2 -N fashion. The Forwarding Engine pulls information off the calling stack by utilizing the type information in the description of the method just called. When walking the description of the method about to be called, it likewise knows the type expected. Knowing both the original type, and the expected type, the Type Description Framework performs a conversion.
In the specific embodiment, two mechanisms are provided for type conversion: object oriented type casting, and neutral type representation. In object oriented type casting, the Type Description Framework can convert among types that are all subclasses of the same type. This is accomplished by the superclass, VTypeData, providing a set of methods which each of the subclasses implements. These methods return the information necessary to construct an instance. This information is sufficient to create any of the subclass types. Thus, to convert, these methods are called on the instance of the type just pulled off the stack. The results provide the information necessary to create an instance of the type which is about to be put on the stack.
In neutral type representation, types know how to convert themselves to one or more neutral types, as well as how to convert from neutral types to themselves. For example, a string type such as a COM Bstr, as a sublcass of string, would have methods to convert itself to either an ASCII string, or a Unicode string, as well as to convert from them to Bstr. Thus, to convert from any string type to any other, the first type converts itself to ASCII or Unicode, and the second type converts from that to itself. Note that the types can agree on which conversion is most efficient, and that conversion only takes place if necessary. Furthermore, those skilled in the art will recognize that the above doesn't preclude the addition of a direct type conversion mechanism between particular object systems (and types) where type conversion optimization is desired.
The Type Description Framework is also used to trigger automatic proxy construction. That is, when an object type is passed, the object needs to be "converted" to an object of the to-be-called object system. Thus a proxy needs to be constructed. The detailed steps involved in proxy construction are described in sections 6) and 7).
5) The Error and Exception Handling Framework: a framework to handle errors and exceptions.
The Error and Exception Handling Framework relies heavily on the type conversion system. As a part of every VFunctionData, a VExceptionData is created. When any exception occurs, the type conversion system converts the exception from the type in one object system to the corresponding type in another. In addition, the type conversion mechanism via the methods in VExceptionData, is responsible for triggering the exception handling system of the foreign object system.
6) The Lifecycle Management Framework: a framework to create, copy, destroy, and (manage the lifecycle of objects) and
7) The Object Exporting Framework: a framework to export object definitions.
Although object lifecycles differ among object systems, the lifecycle of an object in a typical object system is shown in FIG. 8. The process begins when a user asks to create an instance of an object 42. The object system first determines if the factory to create the object is available 43. If the factory isn't available, the object system attempts to start the server 44, as specified in the call to create the object. The object system starts the server application (or loads the appropriate dynamically linked library) and transfers execution to it 45. The server performs initialization and creates factories for all the classes it supports 46. Then, the server registers its factories with the object system, in a process sometimes referred to as "exposing its factories" 47. When the process is completed, the server returns control to the object system 48. The object system then calls a method of the appropriate factory to create an instance of the desired class 49. The factory creates an instance of the object 50, and finally, the instance is returned to the user 51. As the object is utilized, additional references to it may be created 52. The object may be destroyed by any party that has a reference to it 53. Each time a reference to the object is used to destroy it, the server determines if any object cleanup is necessary 54 (e.g. should memory the object is using be de-allocated). Typically, this occurs when the last reference is destroyed.
The system provides interoperability transparently. As a result, it must appear to the object system as a standard object server that follows the standard lifecycle protocols that any server designed specifically for the object system would. The system, or more particularly, the OSA for the object system in which the request takes place, is therefore responsible for items 3, including items 5 and 6, item 8.5, and ensuring that during 10 and 12, all utilization/manipulation of the object is forwarded properly, and transparently to the real object. During 8.5, however, the OSA works with another OSA--the OSA of the object system that the real object is created in, to create a proxy for the real object.
The system provides a framework to perform the above steps--the Object Exporting Framework. Any application/server that contains the system may be 44. As shown in FIG. 9, in performing step 46, the application initializes itself 55, then initializes the system 56. For each class from another object system the application/server wishes to make available in this object system, the ExposeFactory method is called 57 in the OSA of requesting object system. The list of such classes may be hard-coded in the application/server, determined from a persistent store or file, or dynamically determined. The Expose Factory method is called with the VClassData of the class to be exposed, and returns a real factory object from the native object system. It constructs a new factory if required 58, or returns a previously created factory 59. The method also registers the factory with the native object system 60.
Another aspect of exposing classes is registering them in the native object systems "repository." This may involve generating an interface description in a "language" appropriate to the foreign object system (such as Interface Definition Language or IDL in CORBA systems, a Type Library in COM, or C++ header files). It may also require that the OSA use an API to register the class with the object system's repository.
When the object system calls the method of the factory to create an object instance, it is the job of the factory to create a real instance in the foreign object system, then to create a proxy to be returned to the native object system (i.e. the object system which the factory was designed for.) When the OSA constructs the factory, it builds the VClassData for the object in its object system. This VClassData, and the VClassData for the real object (which the OSA was provided in the ExposeFactory method call) are stored with the factory object. When the factory object's method to create the object is called by the object system, the factory object uses the Forwarding Engine to forward the creation call from its object system (using the VClassData it created), to the native object system. When the real object is returned, the factory object constructs a proxy object by calling the AcquireProxy method in the OSA for the foreign object system (more precisely, in the subclass of the Object Exporting Framework provided in the OSA).
The AcquireProxy method is passed the VClassData of the real object, as well as an instance of the object. It constructs a proxy object in the native object system, associating with that object a pointer to all the information required by its OSA. Although the layout of a proxy object is up to the OSA, a typical proxy object is shown in FIG. 10. The proxy object 61 consists of a pointer to its method table 62 (referred to as a viable in C++), as well as a pointer to a metadata object 63. The metadata object consists of a pointer to the method table 64, a pointer to the VClassData of the native object 65, the native object identifier 66, and a pointer to the VClassData of the proxy object 67, as well as path shortening information 68.
The first time an instance of the class is created in the native object system, the AcquireProxy method of an object system typically has to create a method table. It will be understood by those skilled in the art how to dynamically create a method table, and how to associate with each method, sufficient information for the OSA to retrieve which method was called. When the method is called by the object system via the method table, the following steps are typically performed: First, the VFunctionData for the method of the proxy object just called is retrieved. Next, from the metadata of the proxy object, the VClassData of the native object is retrieved, and in turn, the VFunctionData for the corresponding method of the native object is retrieved. These are passed to the forwarding engine for forwarding of the method call.
Construction of a proxy object can be triggered by the user, as in 42, or by the type conversion system. When triggered by type conversion, only AcquireProxy need be called.
When the AcquireProxy method is called, prior to creating a new proxy object, it must check if a proxy object for the native object already exists in this object system. Utilizing a capabilities provided by the system, the method checks its cache of objects. If a proxy already exists it is returned, other wise the system checks if path shortening is required. When multiple systems are working cooperatively to provide object system interoperability, it may be that the object for which a proxy is to be constructed is itself a proxy object. Path shortening refers to the act of not creating a proxy for the proxy, but rather "shortening the path of objects" and creating a proxy for the real object. Those skilled in the art will appreciate that there are numerous path shortening algorithms described in the literature, for example "SSP Chains: Robust, Distributed References Supporting Acyclic Garbage Collection, Shapiro, Dickman, and PlainFosse, Symposium on Principles of Distributed Computing, August 1992", which is hereby incorporated herein by reference.
8) The Mixin Support Framework: a framework to add extra information to the description of any object class, enabling the support in all object systems of features found only in one object system.
Often one object system provides features which aren't available in another object system. In addition, object systems often expect their object to provide certain features. The system provides a general mechanism to handle such interoperability issues called mixins. Mixins are simply objects which may be associated with any other object in the system to extend the functionality the object is capable of providing. A mixin can provide a method which the native object doesn't provide, or override any or all of the native object's methods. As all Frameworks are subclassed from the Mixin Support Framework, mixin objects may be added to any instance of any class provided from the system.
When the forwarding engine walks down the VClassData to retrieve the VFunctionData for the native object's method, it first determines if there is a mixin object associated with the object that provides the method. If so, it calls the Mixin's method instead of the native object's method (if the method even exists for the native object.) The methods of mixin objects can also be triggered to execute prior to, or after any native method call to augment the native object's capabilities. Mixin objects may be associated with the objects known to the system at the class level, or at the instance level. In addition, they are inherited as subclasses of objects are enumerated. Through the Mixin Support Mechanism, a native object need not be aware that its capabilities have been augmented.
9) The OSA Registry Framework: a framework to load, unload, and manage Object System Adapters.
As previously described, Object System Adapters are libraries which package together extensions to the system's default implementations of the above frameworks. An OSA packages everything necessary to fully support bidirectional interoperability among the object system to which it corresponds, and all other object systems with OSAs. The system can dynamically load and unload OSAs using a framework entitled the OSA Registry Framework. The OSA Registry Framework provides the methods to load and unload AdapterNamespaces, and provides the remainder of the system with an object system independent way to determine which object systems are supported. OSAs can be loaded and unloaded while the system is executing, dynamically extending the range of object systems supported.
Further Embodiments of the Present Invention
The invention in a range of other embodiments. In another embodiment, for example, there are provided (A) a system and method to enable the creation of a "universal object", i.e. a single object that appears to be implemented in a plurality of object systems simultaneously, and that can dynamically change which object systems it supports. Such a system enables the creation of "universal objects" in individual, application, and server configurations. Further, such objects may be based upon interpreted or compiled language technology.
In addition to enabling heterogeneous object systems to interoperate, such a system, when used in a slightly modified configuration, enables objects to appear to be implemented in a number of object systems simultaneously. FIG. 11 shows an example of the system being used in such a configuration. In the figure, an individual COM object 69, appears as both a DSOM object 70 in the DSOM-based application 71, as well as an ORBIX object 72 in the ORBIX-based application 73.
There are two configurations in which typical object systems enable their objects to be used: "in process"; and "out of process". See, for example, the OLE 2.0 Programmers Reference, and IBM SOMobjects Developer Toolkit Programmers Reference Manual. When objects are used "in process", they are used as a "dynamic link library" (DLL)--often referred to as a shared library--and execute in the same process space as the software using them. When objects are used "out of process", they execute in the process space of the separate application or server they are within, not within the process space of the software using them.
Although FIG. 11 shows all objects executing in separate processes, it will be obvious to those skilled in the art, that for object systems which support in both in process and out of process objects, the system may be used in either configuration. That is, when the system is used "in process" by an application, the system, including the various frameworks, and the OSA for the object system being used by the application, as well as the proxy objects being used by the application, execute as a DLL in the process space of the application. Note that while the proxies are "in process", the native objects (i.e. the real objects which correspond to the proxies) need not be. They may be in process or in a separate process, as determined by the way they were created in their native object system.
Conversely, while the application using the objects may create them "out of process", even though the system is executing in a separate process, it may create the native object "in process" for efficiency. In this case, in process means the objects are created in the system's process, and not in the process of the application using the objects.
FIG. 12a shows an example of the system enabling a universal object in an individual configuration, while FIG. 12b, and 12c show application and server configurations respectively. In FIG. 12a, 74 is a COM DLL containing three objects. Object 75, is an individual object (i.e. an object not within an application or server) that, through the system, may appear to be from multiple object systems simultaneously. Additional object systems can be supported simply by adding corresponding OSAs. It will be obvious to those skilled in the art that the DLL, 75, may contain one or more individual objects.
FIG. 12b shows an example of the system being used in an application configuration. The system is linked into the application, 76, which includes application objects. In this example, the application has described its objects directly to the system (as would have an OSA), so no OSA is required. The application's objects, through the system, may appear to be from multiple object systems simultaneously. Alternatively, by providing the appropriate OSAs, the same objects may appear to be implemented using different object systems on different platforms. It will be obvious to those skilled in the art that, had the application utilized an object system, an OSA could have been utilized.
FIG. 12c shows an example of the system being used in a server configuration. The characteristic of a server configuration is that the object server, i.e. the process or processes containing objects being used, are in a separate process from the application which is using those objects. In FIG. 12c, the objects, 77, in the server, 78, through he system, may appear to be from multiple object systems simultaneously.
In FIG. 11 through 12c, the objects have been shown as compiled objects, however, they need not be. They may be objects written in an interpreted language, whether fully interpreted, or executed through an intermediate representation. All that is required is the interpreter provide some fundamental mechanism by which its objects may be accessed and manipulated, and that either an OSA be written, or the interpreter describe its objects directly to the system. The utility provided by such an approach is that objects may be written in the language of the interpreter, and those objects may, through the system, appear to be from any object system with a corresponding OSA, thus taking advantage of the rapid development characteristics of an interpretive language environment.
In a further embodiment there are provided (B) an apparatus--either library-based or interactive--to enable the construction of object classes from one or more object systems, including the aforementioned "universal object", where such system in the creation of said object classes, may subclass from, incorporate, or embed instances of objects from a plurality of object systems;
Heretofore, software, either library-based or interactive, which enabled the construction of applications from objects, and/or which enabled the construction of objects have required such objects to follow the single object model supported by the tool. For example, see Microsoft Visual Basic V3.0 Professional Features Book 1, Control Development Guide, 1993. In some cases, dynamic converters have been developed to enable the use of objects from one object system within other an object system, with all the consequent limitations, however, they have not enabled the construction of foreign objects. For example, see Borland C++ V4.0 User's Guide, 1993.
For the apparatus, the system is used in the application configuration, where the application software is that code, hereafter referred to as construction software, that is well known to those skilled in the art, for construction of applications from objects, or for the construction of object classes. To construct applications or object classes, the construction software loads object classes from any object system with an OSA (in addition to any which follow the construction software's own internal object model, if any.) The construction software manipulates the foreign object classes using the system frameworks directly, or alternatively, using the mechanisms from its object model. As a result of the uniform means to manipulate objects from a plurality of object systems provided by the system, the apparatus is enabled.
In another embodiment, there are provided (C) a system and method to enable object classes and objects to be relocated among applications and servers in one or more object systems while the applications and servers are executing, and without disruption of software utilizing said object classes and objects, even if it too is executing.
When used with "in process" objects, or when used with an interpretive language environment in individual, application, or server configurations, the relocation of object classes and objects among applications and servers in one or more object systems is enabled. To move an object class, first, a version of the class must be available in the new location/object system. This is accomplished by:
moving the native object definition. In the case of in-process objects, the DLL they are within must be copied or moved by other means. In the case of an interpretive environment, the source or the intermediate representation must be copied or moved by other means to the new location, and loaded into the appropriate application or server
using the system to expose the class in the new location and/or object system
updating the description of the object class in the system, including its VClassData and other descriptive elements, to reflect its new location and potentially new object system.
If instances of the class already exist and are not to be moved (i.e. only new instances are to be in the new location/object system), the version number of the class must be incremented.
As new instances are created and manipulated, they will be created and manipulated utilizing the new description, thus properly for their new location and potentially new object system. The method applies both to foreign objects, as well as to native objects as long as, for native objects, the system is utilized to perform the creation and manipulation of objects.
Object instances are moved using a similar mechanism. All existing proxies for the instance (i.e. each proxy for each object system and user) must simply have their software description of the native object updated to reflect the new location and/or object system of the instance.
The following is a description of a software architecture according to one embodiment of the present invention. ##SPC1##
It will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the scope of the following invention is limited only by the following claims and their equivalents.
Claims
We claim:
1. A device, for use in a digital computer system which provides for objects of first and second object models and corresponding first and second object systems using respective first and second implementations to implement, respectively, the first and second object models, the device for enabling the first object system to use objects of the second object model, the device comprising: description means for providing a description of an object of the second object model; proxy means for creating a proxy object that is an object of the first object system and that corresponds to the object of the second object model; receiving means for receiving a manipulation of the proxy object, the maximum rotation conforming to the first implementation; and forwarding means for forwarding the manipulation of the proxy object to the corresponding object of the second object model by utilizing the description.
2. A device according to claim 1, for enabling the first object system to use objects of a plurality of object models, wherein: (a) the proxy means comprises means for creating a plurality of proxy objects, each proxy being an object of the first object system and corresponding with an object of one of the plurality of object models; and (b) the forwarding means comprises means for forwarding manipulations of one of the proxy objects to its corresponding object.
3. A device according to claim 2, wherein the device includes means for adding or removing support for object systems and object models, said means for adding or removing support adding or removing support without compiling the device.
4. A device according to claim 2, further comprising a traditional application or object class construction environment, said environment comprising at least one of: means for subclassing from object classes of a plurality of object systems; means for utilizing or incorporating object classes of a plurality of object systems; means for instantiating and embedding object instances of a plurality of object systems; means for constructing objects which can be used according to implementations of a plurality of object systems; means for relocating object classes and objects among application processes, server processes and object systems.
5. A device according to claim 1, wherein the forwarding means further comprises: means for transferring control flow from the digital computer system to the device; means for retrieving semantic information from a call stack of the digital computer system, the semantic information and call stack being in accordance with the proxy object and the first implementation; means for placing the semantic information on a second call stack in accordance with the description of the object of the second object model; means for manipulating the corresponding object in accordance with the manipulation of the proxy object; means for retrieving semantic return information from the second call stack in accordance with the description of the object of the second object model; and means for placing the semantic return information on the call stack of the digital computer in accordance with the proxy object and the first implementation.
6. A device according to claim 5, wherein the means for retrieving semantic information further comprises means for associating the proxy object with the description of the object of the second object model.
7. A device according to claim 6, wherein the means for placing semantic information on the call stack further comprises means for traversing the description of the object of the second object model, the description of the object not being compiled into the device.
8. A device according to claim 5, wherein the means for placing semantic information on the call stack further comprises means for converting semantic types and language types from those used in the first implementation to corresponding semantic types and language types of the second implementation.
9. A device according to claim 8, wherein the means for converting semantic types and language types further comprises: means for converting between object types; and means for triggering creation of a new proxy object.
10. A device according to claim 1, wherein the device further comprises at least one of: means for mapping between fundamental calling mechanisms; and means for mapping between low-level calling conventions, wherein said means for mapping between low-level calling conventions is used in combination with at least one of: means for mapping between differences in semantic types; means for dynamically constructing proxy objects when required; means for mapping between differences in errors and exceptions; and means for mapping between differences in querying for object information.
11. A device according to claim 1, wherein the device further comprises means for mapping between different fundamental calling mechanisms of different object systems.
12. A device according to claim 1, wherein the device further comprises means for mapping between fundamental calling mechanisms and means for mapping between differences in language types.
13. A device according to claim 1, further comprising means for enabling the first object system to use features that are provided by the second object system, but are not provided by the first object system.
14. A device according to claim 1, further comprising means for using features provided by the first object system which require functionality of the proxy object, where such functionality is not implemented by the second object system.
15. A device according to claim 14, wherein the means for using features further comprises: means for associating an object with one or more elements of the description; and means for delegating execution of a feature by the proxy object to the associated object either before responding to a manipulation, instead of responding to a manipulation, or after responding to a manipulation.
16. A device according to claim 1, where the corresponding object is implemented using an interpreted language environment or runtime.
17. A method, for use in a digital computer system which provides for objects of first and second object models and corresponding first and second object systems using respective first and second implementations to implement, respectively, the first and second object models, said method for enabling the first object system to use objects of the second object model, the method comprising: providing a description of an object of the second object model; creating a proxy object that is an object of the first object system and that corresponds to the object of the second object model; receiving a manipulation of the proxy object, the manipulation conforming to the first implementation; and forwarding the manipulation of the proxy object to the corresponding object of the second object model by utilizing the description.
18. A method according to claim 17, for enabling the first object system to use objects of a plurality of object models, wherein: the creating step comprises creating a plurality of proxy objects, each one being an object of the first object system and corresponding with an object of one of the plurality of object models; and the forwarding step comprises forwarding a manipulation of one of the proxy objects to its corresponding object.
19. A method according to claim 18, further comprising the step of organizing objects and classes from a plurality of object systems into a unified namespace.
20. A method according to claim 18, further comprising at least one of the steps of: subclassing from object classes of a plurality of object systems; utilizing or incorporating object classes of a plurality of object systems; instantiating and embedding object instances of a plurality of object systems; relocating object classes and objects among application processes, server processes and object systems; and constructing objects which can be used by implementations of a plurality of object systems.
21. A method according to claim 17, wherein the forwarding step further comprises: transferring control flow from the digital computer system to the device; retrieving semantic information from a call stack of the digital computer system, the semantic information and the call stack being in accordance with the proxy object and the first implementation; placing the semantic information on a second call stack in accordance with a description of the object of the second object model; manipulating the corresponding object in accordance with the manipulation of the proxy object; retrieving semantic return information from the second call stack in accordance with the description of the object of the second object model; and placing the semantic return information on the call stack of the digital computer in accordance with the proxy object and the first implementation.
22. A method according to claim 21, wherein the creating step further comprises associating the proxy object with the description of the object of the second object model.
23. A method according to claim 21, wherein the placing step further comprises converting semantic and language types from the first object system to the second object system.
24. A method according to claim 23, wherein the step of converting semantic and language types further comprises: converting between object types; and triggering a creation of a new proxy object.
25. A method according to claim 17, further comprising: mapping between fundamental calling mechanisms; and mapping between low-level calling conventions, wherein said mapping between low-level calling conventions is performed in combination with at least one of the steps of: mapping between differences in semantic types; dynamically constructing proxy objects when required; mapping between differences in errors and exceptions; and mapping between differences in querying for object information.
26. A method according to claim 17, further comprising mapping between different fundamental calling mechanisms of different object systems.
27. A method according to claim 17, further comprising the steps of mapping between fundamental calling mechanisms and mapping between differences in language types.
28. A method according to claim 17, further comprising the step of enabling the first object system to use features that are provided by the second object system, but are not provided by the first object system.
29. A method according to claim 17, further comprising the step of using features provided by the first object system which require functionality of the proxy object in the case that such functionality is not implemented by the second object system.
30. A method according to claim 29, wherein the step of using features comprises: associating an object with one or more elements of the description; and delegating execution of a feature by the proxy object to the associated object either before responding to a manipulation, instead of responding to a manipulation, or after responding to a manipulation.
31. A method according to claim 17, wherein the corresponding object is implemented using an interpreted language environment or runtime.
32. Computer-executable process steps stored on a computer-readable medium, the steps for use in a digital computer system which provides for objects of first and second object models and corresponding first and second object systems using respective first and second implementations to implement, respectively, the first and second object models, the steps for enabling the first object system to use objects of the second object model, the steps comprising: a providing step to provide a description of an object of the second object model; a creating step to create a proxy object that is an object of the first object system and that corresponds to the object of the second object model; a receiving step to receive a manipulation of the proxy object, the manipulation conforming to the first implementation; and a forwarding step to forward the manipulation of the proxy object to the corresponding object of the second object model by utilizing the description.
33. Computer-executable process steps according to claim 32, wherein the creating step further comprises an associating step to associate the proxy object with the description of the object of the second object model.
34. Computer-executable process steps according to claim 32, for enabling the first object system to use objects of a plurality of object systems, wherein: the creating step comprises a creating step to create a plurality of proxy objects, each proxy being an object of the first object system and corresponding to an object of one of the plurality of object models, and the forwarding step comprises a forwarding step to forward a manipulation of one of the proxy objects to its corresponding object.
35. Computer-executable process steps according to claim 34, further comprising the step of organizing objects and classes from a plurality of object systems into a unified namespace.
36. Computer-executable process steps according to claim 34, further comprising at least one of the steps of: a subclassing step to subclass from object classes of a plurality of object systems; a utilizing step to utilize or incorporate object classes of a plurality of object systems; and an instantiating step to instantiate and embed object instances of a plurality of object systems; a relocating step to relocate object classes and objects among application processes and object systems; a constructing step to construct objects which can be used by implementations of a plurality of object systems.
37. Computer-executable process steps according to claim 36, wherein the corresponding object is implemented using an interpreted language environment or runtime.
38. Computer-executable process steps according to claim 32, wherein the forwarding step further comprises: a transferring step to transfer control flow from the digital computer system to the device; a first retrieving step to retrieve semantic information from a call stack of the digital computer system, the semantic information and the call stack being in accordance with the proxy object and the first implementation; a first placing step to place the semantic information on a call stack in accordance with a description of the object of the second object model; a manipulating step to manipulate the corresponding object in accordance with the manipulation of the proxy object; a second retrieving step for retrieving semantic return information from the second call stack in accordance with the description of the object of the second object model; and a second placing step for placing the semantic return information on the call stack of the digital computer in accordance with the proxy object and the first implementation.
39. Computer-executable process steps according to claim 32, wherein the first placing step further comprises a converting step to convert semantic types and language types from the first object system to the second object system.
40. Computer-executable process steps according to claim 32, wherein the converting step to convert semantic types and language types further comprises: a converting step to convert between object types; and a triggering step to trigger creation of a new proxy object.
41. Computer-executable process steps according to claim 32, further comprising: a mapping step to map between fundamental calling mechanisms; and a mapping step to map between low-level calling conventions, wherein said mapping between low-level calling conventions is performed in combination with at least one of the steps of: a mapping step to map between differences in semantic types; a constructing step to dynamically construct proxy objects when required; a mapping step to map between differences in errors and exceptions; and a mapping step to map between differences in querying for object information.
42. Computer-executable process steps according to claim 32, further comprising a mapping step to map between different fundamental calling mechanisms of different object systems.
43. Computer-executable process steps according to claim 32, further comprising a mapping step to map between fundamental calling mechanisms and a mapping step to map between differences in language types.
44. Computer-executable process steps according to claim 32, further comprising a using step to use features that are provided by the second object system but are not provided by the first object system.
45. Computer-executable process steps according to claim 32, further comprising a using step to use features provided by the first object system which require functionality of the proxy object in the case that such functionality is not implemented by the second object system.
46. Computer-executable process steps according to claim 45, wherein the step of using features comprises: an associating step to associate an object with one or more elements of the description; and a delegating step to delegate execution of a feature by the proxy object to the associated object either before acting on a manipulation, instead of acting on a manipulation, or after acting on a manipulation.
47. A device, for use in a digital computer system providing objects of first and second object systems using respective first and second implementations which implement respective first and second object models, the device for enabling the first object system to use an object of the second object system, the device comprising: description means for providing a description of object aspects, object system aspects and object manipulations, said description describing first semantic types, first aspects, or first implementations that are supported by the first object system and not by the second object system and describing second semantic types, second aspects or second implementations supported by the second object system and not by the first object system; and forwarding means for forwarding a manipulation of a first object, the manipulation in accordance with the first implementation, to the second object by utilizing the description, wherein the first object corresponds to the second object.
48. A device according to claim 47, wherein the forwarding means comprises mapping means to map the first semantic types and the first implementations to the second semantic types and the second implementations dynamically during execution of the device.
49. A device according to claim 47, wherein the forwarding means comprises mapping means to build steps for mapping the first semantic types and first implementations to the second semantic types and second implementations and execution means for executing the steps for mapping.
50. A method, for use in a digital computer system providing objects of first and second object systems using respective first and second implementations which implement respective first and second object models, the method for enabling the first object system to use an object of the second object system, the method comprising the steps of: providing a description of object aspects, object system aspects and object manipulations, said description describing first semantic types or first implementations that are supported by the first object system and not by the second object system and describing second semantic types or second implementations supported by the second object system and not by the first object system; and forwarding a manipulation of a first object, the manipulation conforming to the first implementation, to the second object by utilizing the description, wherein the first object corresponds to the second object.
51. A method according to claim 50, wherein the forwarding step comprises mapping the first semantic types and the first implementations to the second semantic types and the second implementations dynamically during execution of the method.
52. A method according to claim 50, wherein the forwarding step comprises building steps for mapping the first semantic types and first implementations to the second semantic types and second implementations and executing the steps for mapping.
53. Computer-executable process steps stored on a computer-readable medium, the steps for use in a digital computer system providing objects of first and second object systems using respective first and second implementations which implement respective first and second object models, the steps for enabling the first object system to use an object of the second object system, the steps comprising the steps of: a providing step to provide a description of object aspects, object system aspects and object manipulations, said description describing first semantic types or first implementations that are supported by the first object system and not by the second object system and describing second semantic types or second implementations supported by the second object system and not by the first object system; and a forwarding step to forward a manipulation of the first object, the manipulation conforming to the first implementation, to the second object by utilizing the description, wherein the first object corresponds to the second object.
54. Computer-executable process steps according to claim 53, wherein the forwarding step comprises mapping the first semantic types and the first implementations to the second semantic types and the second implementations dynamically during execution of the method.
55. Computer-executable process steps according to claim 53, wherein the forwarding step comprises building steps for mapping the first semantic types and first implementations to the second semantic types and second implementations and executing the steps for mapping.
56. A method for utilizing a foreign object of a foreign object model implemented by a foreign object system in the case that the foreign object is called by a native object system implementing a native object model, the method comprising the steps of: creating a proxy object of the native object model, said proxy object corresponding to the foreign object; extracting semantically meaningful information from a call stack of the native system; transferring the semantically meaningful information to a call stack of the foreign system; and calling the foreign object.
57. A method according to claim 56, wherein said extracting step comprises utilizing a description of the foreign object to determine steps required to extract semantically meaningful information from a call stack of the native object system in accordance with the description of the proxy object, and wherein said transferring step comprises performing the steps required to extract the semantically meaningful information and transferring the semantically meaningful information to a call stack of the foreign object system in accordance with the description of the foreign object.
58. A method according to claim 57, wherein said extracting step further comprises dynamically loading a device in order to utilize the description.
59. A method according to claim 57, wherein, in the transferring step, the semantically meaningful information is transferred to a call stack of any of a plurality foreign object systems.
60. A method according to claim 57, wherein said transferring step further comprises converting data types of the semantically meaningful information extracted from the call stack of the native system to data types of the foreign object model before transferring the semantically meaningful information to the call stack of the foreign system.
61. A method according to claim 57, further comprising extracting semantically meaningful return information from the call stack of the foreign system by utilizing a description of the foreign object and transferring the return information from the foreign object to the call stack of the native system.
62. A method according to claim 57, wherein the foreign object provides functionality to the native object system which cannot be provided by an object of the native object system.
63. A device for utilizing a foreign object of a foreign object model implemented by a foreign object system in the case that the foreign object is called by a native object system implementing a native object model; comprising; creating means for creating a proxy object of the native object model, said proxy object corresponding to the foreign object; extracting means for extracting semantically meaningful information from a call stack of the native system; transferring means for transferring the semantically meaningful information to a call stack of the foreign system; and calling means for calling the foreign object.
64. A device according to claim 63, wherein said extracting means comprises utilizing means for utilizing a description of the foreign object to determine steps required to extract semantically meaningful information from a call stack of the native object system in accordance with the description, and wherein said transferring means comprises performing means for performing the steps required to extract the semantically meaningful information and transferring means for transferring the semantically meaningful information to a call stack of the foreign object system in accordance with the description of the foreign object.
65. A device according to claim 64, wherein said extracting means further comprises loading means for dynamically loading a device in order for the utilizing means to utilize the description.
66. A device according to claim 64, wherein said transferring means transfers the semantically meaningful information to a call stack of any of a plurality foreign object systems.
67. A device according to claim 64, wherein said transferring means further comprises converting means for converting data types of the semantically meaningful information extracted from the call stack of the native system to data types of the foreign object model before transferring the semantically meaningful information to the call stack of the foreign system.
68. A device according to claim 64, wherein said extracting means extracts semantically meaningful return information from the call stack of the foreign system by utilizing a description of the foreign object and said transferring means transfers the return information from the foreign object to the call stack of the native system.
69. A device according to claim 64, wherein the foreign object provides functionality to the native object system which cannot be provided by an object of the native object system.
70. Computer-executable process steps stored on a computer-readable medium, the steps for utilizing a foreign object of a foreign object model implemented by a foreign object system in the case that the foreign object is called by a native object system implementing a native object model, the steps comprising: a creating step to create a proxy object of the native object model, said proxy object corresponding to the foreign object; an extracting to extract semantically meaningful information from a call stack of the native system; a transferring step to transfer the semantically meaningful information to a call stack of the foreign system; and a calling step to call the foreign object.
71. Computer-executable process steps according to claim 70, wherein said extracting step comprises a utilizing step to utilize a description of the proxy object so as to determine steps required to extract semantically meaningful information from a call stack of the native object system in accordance with the description of the foreign object, and wherein said transferring step comprises a performing step to perform the steps required to extract the semantically meaningful information and to transfer the semantically meaningful information to a call stack of the foreign object system in accordance with the description of the foreign object.
72. Computer-executable process steps according to claim 71, wherein said extracting step further comprises a loading step to dynamically load a device in order to utilize the description.
73. Computer-executable process steps according to claim 71, wherein, in the transferring step, the semantically meaningful information is transferred to a call stack of any of a plurality foreign object systems.
74. Computer-executable process steps according to claim 71, wherein said transferring step further comprises a converting step to convert data types of the semantically meaningful information extracted from the call stack of the native system to data types of the foreign object model before transferring the semantically meaningful information to the call stack of the foreign system.
75. Computer-executable process steps according to claim 71, further comprising a second extracting step to extract semantically meaningful return information from the call stack of the foreign system by utilizing a description of the foreign object and a second transferring step to transfer the return information from the foreign object to the call stack of the native system.
76. Computer-executable process steps according to claim 71, wherein the foreign object provides functionality to the native object system which cannot be provided by an object of the native object system.
77. A device, for use in a digital computer system providing a plurality of processes and object systems, the device for enabling a native object system having a native implementation for implementing a native object model and located in a first process to use an object located in a second process via a foreign object system using a foreign object model, the device comprising: description means for providing a description of the object; proxy means for creating a proxy object conforming to the native object system that corresponds with the object located in the second process; receiving means for receiving a manipulation of the proxy object, the manipulation conforming to the native implementation; and forwarding means for forwarding the manipulation of the proxy object to the corresponding object by utilizing the description and the foreign object system.
78. A method, for use in a digital computer system providing a plurality of processes and object systems, the method for enabling a native object system having a native implementation and located in a first process to use an object located in a second process via a foreign object system using a foreign object model, the method comprising: providing a description of the object; creating a proxy object conforming to the native object system that corresponds with the object located in the second process; receiving a manipulation of the proxy object, the manipulation conforming to the native implementation; and forwarding the manipulation of the proxy object to the corresponding object by utilizing the description and the foreign object system.
79. Computer-executable process steps stored on a computer-readable medium, the steps for use in a digital computer system providing a plurality of processes and object systems, the steps for enabling a native object system having a native implementation and located in a first process to use an object located in a second process via a foreign object system using a foreign object model, the steps comprising: a providing step to provide a description of the object; a creating step to create a proxy object conforming to the native object system that corresponds with the object located in the second process; a receiving step to receive a manipulation of the proxy object, the manipulation conforming to the native implementation; and a forwarding step to forward the manipulation of the proxy object to the corresponding object by utilizing the description and the foreign object system.
80. A device according to claim 1, 47 or 77, wherein an implementation includes fundamental calling conventions and low-level calling conventions.
81. (Amended) A method according to claim 17, 50 or 78 wherein an implementation includes fundamental calling conventions and low-level calling conventions.
82. Computer-executable process steps according to claim 32, 53 or 79, wherein an implementation includes fundamental calling conventions and low-level calling conventions.
83. A device according to claim 1, 47, 64, or 77, wherein a description describes both semantic information and implementation information.
84. A device according to claim 83, wherein the device provides an application programming interface to enable a system or an object to be described to the device.
85. A device according to claim 83, wherein the device provides an application programming interface to a plurality of programming languages, the application programming interface enabling elements of a programming language to emulate an object of an object system.
86. A method according to claim 17, 50, 57, or 78, wherein a description describes both semantic information and implementation information.
87. A method according to claim 86, further comprising providing an application programing interface to enable an object system or an object to be described.
88. A method according to claim 86, further comprising providing an application programming interface to a plurality of programing languages, the application programming interface enabling elements of a programing language to emulate an object of an object system.
89. Computer-executable process steps according to claim 32, 53, 71, or 79, wherein a description describes both semantic information and implementation information.
90. Computer-executable process steps according to claim 89, further comprising a providing step to provide an application programming interface to enable an object system or an object to be described.
91. A method according to claim 90, further comprising a providing step to provide an application programming interface to a plurality of programming languages, the application programming interface enabling elements of the language to emulate an object of an object system.
92. A device according to claim 47, 63, or 77, further comprising means for organizing objects from a plurality of object systems into a unified namespace.
93. A method according to claim 50, 57, or 78, further comprising organizing objects from a plurality of object systems into a unified namespace.
94. Computer-executable process steps according to claim 53, 70 or 79, further comprising an organizing step to organize objects from a plurality of object systems into a unified namespace.
95. A device according to claim 47, 63, or 77, further comprising means for dynamically relocating objects among application processes, server processes or object systems.
96. A method according to claim 50, 57, or 78, further comprising dynamically relocating objects among application processes, server processes or object systems.
97. Computer-executable process steps according to claim 53, 70, or 79, further comprising a relocating step to dynamically relocate objects among application processes, server processes or object systems.
98. A device according to claim 2, further comprising means for organizing objects and classes from a plurality of object systems into a unified viewing space.
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