| 摘要 |
A method and apparatus are provided for extending the behavior and attribute s of applications designed using a fourth generation language (4GL) programmin g tool. Specifically, a 4GL programming tool is provided that allows applicati on designers to specify the implementation classes of the components that are used in the applications that they design using the 4GL programming tool. Th e implementation classes thus specified may define attributes and behaviors no t supported by the corresponding component implementations provided with the 4 GL programming tool. During runtime, methods in the specified implementation classes are invoked. To correctly invoke the methods of user-specified implementation classes, the interfaces of the methods must be known to the entity performing the invocations. Therefore, according to one aspect of the invention, all component implementations that are to be used by the application, including both the "standard" component implementations provide d with the 4GL programming tool and the "custom" component implementations specified by the application designer, implement a common interface.
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