7.3 to meet the arguments
Discussed in Section 7.2 to achieve the basic traceability, for many organizations is an important development step. Indeed, the change in organizational culture, using even this simple method, which itself may be a big step. However, there is always more we can do.
In the example shown in Figure 7.1, three system requirements to some extent to fully meet customer needs. However, by non-experts to test this assertion is difficult, because there is no reason given.
Better approach is for each user needs to provide a "meet the argument." As shown in Figure 7.1 for the basic traceability, the only information provided to meet the needs of the three systems act as a role in the argument, but not exactly what direction what is the argument.
Rich traceability is a way to capture the argument to meet. This method is the user needs and system requirements corresponding to another description, shown in Figure 7.3.
Not only to meet the argument described in text mode, but also the use of logic operators describe the way the combined system requirements:
鈼?and (&) operator to meet the argument that the user needs requires the establishment of all system requirements;
鈼?or (or) operator to meet the argument that the user needs requires the establishment of an arbitrary system requirements.
Figure 7.4 shows an example or to provide heating cycle, or gas ring, or two laps, all meet. Note that the argument of the two-logic structure.
Now offers more and more are to meet the needs of information users, if not the domain experts can assess important aspects of the argument. Text help to assess the accuracy and integrity of the logical argument. Operator to make the argument structure more accurately.
Please pay special attention, for Figure 7.2, a collection of system requirements that alternative solutions is very clear, and for Figure 7.4, the expression of this fact is very specific. If you can not provide electric circle, the circle continues to meet the demand through the gas.
On the first taste of the rich traceability through the "West Coast Railway Modernization" project, Praxis Critical System company needs a team proposes a management process and the use of the "design evaluation" of the data model. The same concept can also be found in a variety of similar methods, which meet the arguments have different terminologies, such as "needs more detail", "the basic principles of traceability," "strategy" and so on.
In addition to lower demand, the argument may also depend on to meet a lot of content. Figure 7.5 shows a use of "domain knowledge" to support the argument of the case. Domain knowledge about the real world, a fact or hypothesis does not itself bound solution. In this case, domain knowledge description is to satisfy the basic part of the argument, said box with ramp.
Capture this assumption is important because the real world as well as on assumptions made by the real world are changing. Once captured this assumption, you can use to export analysis to understand the changing assumptions on the system ability to meet their needs.
One such example is the New York subway. 70 years a series of accidents occurred due to incorrectly assume that the train's braking distance. Although initially been confirmed, but after a few years later become heavier trains, braking distance increases, the old assumptions no longer valid. Although the initial operation of the signal system is correct, but no evolution, changed assumptions imply a specific time from the start, signaling system no longer meet the demand.
Through effective traceability can provide records and the ability to track the role of this assumption.
Non-demand information to meet the arguments of another example of work from modeling. Meet the arguments often through complex modeling
Activities of export, the complete details are too detailed, can not capture rich traceability.
Figure 7.6 shows an example from a railway project, which satisfy the argument depends on the use of a tool called VISION timetable for modeling complex activities. Derived through this modeling tool subsystem a set of assumptions and requirements, according to the formation of rich traceability structure of the document. The reference model box with rounded corners, said.
In this example, the need to reconsider the analysis of the modeling activities will obviously impact.
Rich traceability of course, can also be used for multi-demand or object. Figure 7.7 shows three levels and between levels of traceability.
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