System Context Diagram

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. 

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. 

Figure 2. Overall system context of the pheromone detection system in moths (shown in centre). AL is the antennal lobe, MB the mushroom bodies and, LH the lateral horn. This schematic shows the animal in an input/output diagram with respect to its environment.

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. 

System Context and Interface diagrams which model all system constituents including human interactions and the environment ... 

After you analyze the business context, the typical next steps are to redesign the business interactions and to install a new component. This may involve redrawing the diagrams if the business process is to be much changed, or you may need only to refine the picture to sufficient detail to see how the abstractly specified business processes are supported by the system you intend to build. (More on the procedure will follow in the next chapters.)... 

Imperfect Bifurcation. In the context of spatial selforganization, the bifurcation diagram of a system is a plot of the amplitude of a pattern as a function of the various control parameters. For the cell in a plane parallel applied field of strength E and with some system parameter X (as a bath concentration or as in (22)), the pattern amplitude can be described by the g s in (23-30) and especially (29). 

In the same context, the metal sulfide substrate is a component of an Me-S-HjO system which may be far from equilibrium and which may contain a number of metastable molecular and ionic species. While the availability of the relevant thermodynamic data, especially for metastable systems, is far from complete, Eh-pH diagrams have been constructed in connection with... 

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