The rules of the language typically constrain how models can be created: they
de?¬?ne the legal values, relationships between concepts, and how certain concepts
should be used. The rules can vary from strict model correctness rules and consistency
checking to rules that guide rather than enforce a particular way of modeling. Once the
rules are de?¬?ned, the modeling language??”enacted by the supporting tool??”
guarantees that all developers follow the same domain rules. The rules again
signi?¬?cantly reduce the possible design space??”the kinds of applications that can be
written with this language??”and help ensure designers only make appropriate
applications. Should the range of applications need to be extended, the modeling
language can of course be extended later. We discuss language evolution and the
de?¬?nition of rules in more detail in Chapter 10.
Semantics Every modeling concept has some meaning, semantics. When we add
an element into a model or connect elements together we create meaning. InDSM, the
semantics of the modeling language come to some extent directly from the problem
domain. An example helps here: if we are developing an infotainment system for a car,
the modeling concepts, such as a ???knob,??? a ???menu,??? and an ???event???, already have wellde
?¬?ned meanings within the application domain.
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