A Dynamic Software Evolution by Metamodel Change

Every long-time running software system is sooner or later subject of a change. The most common reasons are different requests for a bug fixing or adding a new functionality. Software maintenance forms bigger part of software’s lifetime. Before applying a change, it is essential to correctly understand current state of affected system. Without all relevant information about both – system as whole and implementation details, a change can introduce new bugs or even break functionality of the system. In the paper we present contribution to program comprehension and following program change. Our method utilizes metalevel architectures to separate legacy application from evolution tool. The tool, placed in metalevel, uses aspect-oriented techniques to introduce a new code in the base level legacy application. This code manages casual connection between base level and metamodel, which is automatically created in metalevel. According to the base level program behavior, the metamodel is created and/or updated. Depending on the metamodel change, the base level program is extended with code which affects its functionality. Since the metamodel describes related implementation in higher level of abstraction, the method improves program comprehension and simplifies change.