CHAPTER 2

UML Architecture

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In This Chapter

  • Understanding the four-layer architecture approach
  • Exploring the structure of UML 1.4
  • Examining the key features of UML 1.4
  • Exploring the structure of the UML 2.0
  • Examining the key features of UML 2.0

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In every version of the UML, the authors have applied a four-layer metamodel architecture. Although time pressures kept the original specification's implementation from being all it needed to be for the long term, UML 1.4 successfully adheres to the four-layer concept. The authors of 2.0 have taken great pains to expand on the four-layer approach, and their effort results in an improved implementation of it. I'll step through both UML 1.4 and 2.0 versions after I discuss the significance of the four-layer metamodel architecture.

The Four-Layer Metamodel Architecture

Understanding the four-layer model will be easier if we start with an example using two layers and build up. To do this, though, I need to use Class diagram notation. If you are unfamiliar with this Class diagram notation, you may want to read Chapters 5 and 6 first, and then come back here.

Chapter 1 explained that the MOF is a metamodel, a model that defines the concepts used to build models. When you show the relationship between the metamodel and the model, as in Figure ...

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