The IT industry is suffering from severe budget overruns and ill-performing IT services. Some of the problems that have caused IT project disasters could have been anticipated in the early project phases and mitigated in the project follow-up by modeling the system context and the software design. This chapter shows how to make models of varied views and at varied levels of abstraction to guide software design choices. Models of the enterprise provide understanding of the objectives. Models of the specification provide understanding of system performance and behavior. Models of the design provide understanding of design choices, such as the allocation of functions, resource usage, selection of mechanisms for communication, instantiation, synchronization, security, exception handling, and many more aspects. High-level models are simple models with the primary goal to support understanding, analysis, communication, and decision making. The models have various complementary representations and formats, e.g. visual diagrams, mathematical formulas, and quantitative information and graphs. Model-driven and model-based engineering approaches focus mostly on artifacts to analyze and synthesize software and hardware. High-level models complement model driven approaches by linking the system context to more detailed design decisions. High-level modeling as discussed in this chapter is based on research performed in industrial settings; the so-called industry-as-laboratory approach.
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