Their use could be supported with
the previously described function calling capability: they could be de?¬?ned as ready
library services that are used in the designs with the Library concept.
Finally, a separate comment element was added to the language to allow
attaching free form textual descriptions to models. This concept was extended with
model checking capabilities: its representation in the design showed the results of a
selected model checking report. Figure 8.4 shows a metamodel for the modeling
language showing the legal connections between different object types of the
language.
8.3.2 Modeling Rules
The basic metamodel included language constructs and their connections, but these
did not cover the domain rules and the mobile UI programming model. Extending the
language with rules would prevent errors and enable design consistency at modeling
time. These were considered important as most application developers, similar to
those using plain Python for S60, don??™t have much experience of mobile application
development.
Rules Checked During Modeling The behavioral part of the application was
largely modeled using directed relationships for specifying user navigation, view
170 MOBILE PHONE APPLICATIONS USING A PYTHON FRAMEWORK
structure, and access to the phone services. Here, general rules from state machines
were reused and extended:
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