The present invention relates to software system architecture, and in particular to a method of providing dynamic extensibility of software components, such as object classes.
In a traditional computing environment, executable components make requests of other executable components. In some instances, knowing which requests a component supports is built directly into all components that may make requests of it. In other cases, a component may provide the ability to answer queries about the requests that it supports. The latter case has the advantage of not requiring all potential clients to possess complete knowledge of the supported operations of all other components. This is well known and well understood technology.
Traditionally, when a component receives a request that it does not recognize, it responds by sending an error back to the calling component. This often results in the calling component cascading the error up the call chain until the application fails.
Systems such as Common Lisp, Small Talk, and Forth provide dynamic binding of software components. However, such systems perform such dynamic binding at installation or class definition time, before the components are actually required. Thus, a large resource footprint is required.
A Domain Name Server (DNS) has the ability to pass on a request to resolve a Domain Name to a more knowledgeable server. However, DNS's do not have the ability to upgrade their functionality if they receive a request in a format they cannot process, but simply pass a domain name on if it is not in the list it has stored.
The CORBA Dynamic Invocation Interface (DII) and Dynamic Skeleton Interface (DSI) allow the dynamic dispatch of requests on software components, so that changes to other components can be utilized at runtime; however, they do not cover the dynamic extensibility of executable content in a server component. The server component will return an error if it receives a request it cannot process.