Aspect-Oriented Model For Real-Time Systems Based On UML And Formal Methods

Separation of Concerns is a common, widely used principle in software engineering. It suggests that a complex problem that is hard to understand be divided into a series of smaller problems that are less complex and easier to comprehend. These smaller problems may than be solved one at a time and finally may be put back together again to solve the big problem. Developing software this way leads to a greater comprehensibility, maintainability, adaptability, and reusability of programs since problems are cut down to units whose size is perceptible by human minds and that may be generalized to suit various needs.Real-Time systems have been applied in every area widely, but they have many non-functional requirements, such as the real-time requirement, which cross cut the whole system modules. That may cause the code tangle and scatter, make the systems hard to design, reuse and maintain, and affect performance of systems badly.AOP is a new software development paradigm, which could attain a higher level of separation of concerns in both functional and non-functional matters by introducing aspect, for the implementation of crosscutting concerns. Different aspects can be designed separately, and woven into system. This way can not only solve the architect's under/overdesign dilemma of crosscutting in OOP, but also solve the problems stated above.There are many implementations of aspect-oriented programs recently, such as AspectJ, but no modeling language is available for the design of AOP. So we express the AOP using UML and formal methods, and establish the Aspect-Oriented Software Design Model correspondingly to model real-time systems.Firstly, we introduce the technologies of real-time systems, aspect-oriented software design, and UML, summarize the expression of real-time in UML, and discuss the time model of UML.Secondly, we propose a new aspect-oriented software design model called AOSD-UML which expresses the AOP by extending UML, designs profile of AOSDin the meta-model of UML, and model the aspect-oriented systems from several parts such as structure, behavior and aspect weaving and so on. For demonstration purposes, a simple sample application is modeled in this work with the help of AOSD-UML. Class diagrams model the structure model of aspects, static relationship between aspects and core component, and relationship among aspects. Collaboration diagrams design dynamic behaviors of aspects and core component, while statecharts refine those behaviors and realize the aspects weaving. In order to model real-time systems, we extend the real time into AOSDM-UML with integrating real-time logic, and an elevator example illustrates the model.Finally, in order to model real-time systems with formal methods, we design the different aspects of the system by different formal languages according to the aspect-oriented technology. The functional aspects can be described by LOTOS, while the non-functional aspects by SQTL. A labeled transition system and event scheduler can be defined to weave the aspects with timed automata. According to characteristic of distributed real-time systems, we separate the time aspect into three sub-aspects in advance, which are deterministic time sub-aspect, undeterministic time sub-aspect and fuzzy time sub-aspect. Those sub-aspects are designed by SQTL and FTN etc. After all the sub-aspects are implemented, they are translated into timed automata and woven into the system, and realize the real-time feature.