The UML is a complex language. The current specification of the language has three parts
- Superstructure (758 pages)
- Infrastructure (226 pages)
- Interchange (132 pages)
This text is so dense that it is commonly referred to as the "hairy underbelly" of the UML. SysML is even worse: it contains about 80 of the UML specifications and adds a good bit more (272 pages). It also has a number of subtle and complicated features. This has been a barrier to acceptance and usage of the SysML in some systems engineering environments.
However, the complexity of the full specification should not be a barrier to the adoption and use of the modeling language. An engineering team can get approximately 80% of the benefits of modeling with a core 20% of the language. I have created a SysML Profile called Minimal SysML. It includes a subset of features. Other features and views defined by the SysML can be incrementally adopted once the core subset is understood, but only when needs for more advanced features arise.
The language subset contains fewer diagrams than the set defined with the SysML specification and some of the diagrams are simplified in terms of the elements they contain. The core diagrams are:
- Use case diagram
- Block diagram (block definition diagram and external block diagram are variants)
- Activity diagram
- State diagram
- Sequence diagram
Some of the diagrams removed include:
- Requirements diagram: a "virtual diagram" that really isn't a diagram type at all
- Package diagram: a use of a block diagram
- Parametric diagram: used to model parametric constraints.
Some elements within the support diagrams are also removed:
- Block diagrams: retain proxy ports but lose full ports
- State machines: lose history pseudo state and junction connector
- Sequence diagrams: omit create, destroy, found and lost messages, execution occurrence, and reply messages. Activity diagrams lose action pin, call operation, interruptible regions, and flow final.
This subset supports almost all system engineering workflows, such as requirements modeling, use case functional analysis, architectural specification, and interface definition. As mentioned, as comfort permits – and need arises – the other views and elements can be incrementally added back. In the meantime, you will have a simpler language that allows you to do almost all the required engineering.
- Learn more about Rational System Architect:
- To learn more about the tool for collaborative, model-driven development for embedded systems, start with the Rational Rhapsody product line overview and the Rational Rhapsody page on IBM developerWorks. Also see the Rational Rhapsody 7.6 information center and the Changing the location of help content to get a local copy of the documentation.
- Explore the various versions, too: IBM Rational Rhapsody Architect for Software, a visual development environment for embedded systems and software
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