In SysML, the UML class diagram is called block
defi nition diagram .
?– The UML composite structure diagram is called internal block diagram in
SysML.
?– Item fl ows between elements in the internal block diagram can be
modeled.
?– Continuous functions are supported by action and object nodes in activity
diagrams, and Enhanced Functional Flow Block Diagrams (EFFBD) are
also supported.
?– New diagram types were added: the requirement diagram and the parametric
diagram.
?– The ISO AP-233 data format was added to support the exchange of data
between different tools.
4.1 History
SysML is a very young language, and its history is accordingly short. Nevertheless
it is rewarding to have a look at how it was born to better understand its objectives
and structures.
UML has been used in many systems engineering projects, mainly those heavily
inclined to the software side, but it lacked a standardized extension. Such an
extension was required to satisfy special needs, including, for example, ways to
model different forms of requirements, support for continuous functions, and
decomposition structures.
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