FIGURE 2-28
Interaction points.
System
Identify system
interaction points
System context
[interaction points]
System context
62 CHAPTER 2 The Pragmatic SYSMOD Approach
Interestingly, ROOM does not know interfaces in the sense UML does. The two
concepts of port and interface have both been part of a language only since the
introduction of UML 2.0. It is then a task of the approach models to cleanly separate
the two concepts.
SysML distinguishes between a standard port and an object fl ow port. A standard
port is used to supply or request services. Such a port normally has synchronous
character, i.e., it is a point over which a request is started and where the
sender of the request waits for the result from the receiver. In contrast, object
fl ow ports transport information to and from the system. They often have asynchronous
character, e.g., information from external sensors. We don ??™ t want to look
at these details in this early stage of our approach. We will use only standard ports
that comply with the UML-2 ports for now, and do without modeling interfaces
for the sake of simplicity, since we are currently interested only in the interaction
points themselves.
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