Known Uses

The External Polymorphism pattern has been used in the following systems:

• The ACE framework uses the pattern to register ACE objects in a Singleton in-memory object database. This database stores the state of all live ACE objects and can be used by debugger to dump this state. Since many ACE classes are concrete data types it was not possible to have them inherit from a common root base class containing virtual methods.
• The DV-Centro C++ Framework for Visual Programming Language development from DV Corporation uses the External Polymorphism pattern to create a hierarchy around unrelated internal system classes.
• The Universal Streaming System from ObjectSpace's Systems<Toolkit> uses the External Polymorphism pattern to implement object persistence via streaming.
• A variation of this pattern was independently discovered and is in use at Morgan Stanley, Inc. in internal financial services projects.
• This pattern has been used in custom commercial projects where code libraries from disparate sources were required to have a more common, polymorphic interface. The implementation of the pattern presented a united interface to classes from a locally-developed library, the ACE library, and various other ``commercial'' libraries.
• The idea for the signature adapter came from usage in the OSE class library. In OSE, template functions are used to define collating algorithms for ordered lists, etc.