Based on UML sequence diagram of the Unified Modeling Language (UML, Unified Modeling Language) specification is given a formal definition and syntax descriptions, and further analysis of the object between the sending and receiving messages consistency. Finally, the analysis of case-based reasoning process, the characteristics of UML sequence diagrams for further explanation. This UML sequence diagram based model transformation and model validation provided the necessary precondition for the software system can be used to understand the completeness of the structure and construction of visual modeling tools.