Context diagrams

The result should show how the business works, with the component of interest being one element. A component can (and usually does) play several distinct roles, providing a different interface to each of several other objects, or actors, as they aie often called in this context as usual, they may be other pieces of software, people, or equipment. A collaboration diagram can be used to illustrate the different interactions (see Figure 5.8). This is often called a system context diagram it is traditional to draw the external roles as stick figures, although type boxes are also OK. 

Figure 6.13 Context diagram (collaboration) for one software component.

Functional requirements on the system Usually in the form of a system context diagram with use cases and scenarios... 

A business improvement effort may be triggered by the installation or upgrade of a software system, a perceived quality problem in business performance, or the hiring of a new senior executive. Although the explicit request may be simply to work on a software project, the analyst s scope often expands to include business improvement. This is part of what the system context diagram (see Pattern 15.5, Make a Context Model with Use Cases) is about—the computer system as one element in the design of a business process. 

In such cases, most of the work illustrated in this section should already have been done and in considerably more formality than shown here. In fact the relationship betwen our system and its context is then exactly that of a Major Component as illustrated below in Section 14.3, System context diagram, on page 656. 

In Catalysis, a collaboration is defined as a set of related actions between objects. UML provides one definition for collaboration and then uses the term collaboration diagram to depict a sequence of messages that result from a particular triggering request to an object. We considered the term use case diagram but have not seen that used consistently for anything except the actor-level context diagram of a system. 

DFDs allow the same system to be examined at many levels of detail, from the context diagram level through whatever level the development team chooses to stop at. 

Fig. 18.7 Context diagram and data flow in collaboration hub (reproduced with kind permission from M. Fink 2014)...

Fig. 18.9 Context diagram of secure data exchange platform [42]...

In addition, a novel function of the context diagram was to identify the experience and expertise required from the members of the hazard identification panel. Participants were allowed to express their opinion and encouraged to take an active part in the sessioa... 

To use the predicate patterns for describing the dependability requirements of a concrete problem, the domains of the problem diagram (and in the context diagram) must be derived from the domains given in the dependability patterns. They must be described in such a way that it is possible to demonstrate that the dependability predicate holds for all objects of this class. The parts of the pattern s textual description printed in bold and italics should be refined according to the concrete problem. 

Fig. 4. CACC context diagram after mechanisms have been selected...

Diagrams are a good means to illustrate these deliverables the environmental model is illustrated by a context diagram showing the connections with the environment, the behavioral model is supported by data-flow diagrams showing the functions and internal structure and also for simulations often graphical tools are used. 

Figure 30.3 shows the context diagram of the model to be built. 

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