Tools and Techniques for Requirements Engineering and Management - Requirements Engineering and Management for Software Development Projects - page 189

The data description is absent and it needs to be obtained and documented using
other means. The use case diagrams are indeed simple but it is difficult to represent
complicated logic in large complex software system.
In the Table 13.2 , I have not included the description for all the use cases
included in the Fig. 13.11 . Only one use case is described as an example. Using the
format given in Table 13.2 other use cases can be described.
Use case diagrams coupled with use case descriptions are used to capture
requirements for the projects by many organizations.
13.5.3 Sequence Diagrams
Sequence diagrams depict the sequence of operations between classes or objects.
Sequence diagrams are used more to model the design but can also be used to
model requirements. Sequence diagrams depict the classes/objects included in the
scenario and the interactions between them along with the sequence.
Objects are depicted using rectangles, the actors are depicted using the stickman,
and the messages are depicted using solid lines and dotted lines. Figure 13.12 depicts
a sample sequence diagram for the procurement system.
13.5.4 Statecharts
Statecharts are used to model the behavior of the entities in the system. Usually,
statecharts are more often used to model the design of the system but they could
also be used to model the behavior of the use cases
A very simple statechart is depicted in Fig. 13.13 . In this statechart, the
requirement of material is recognized and when the event of Production Executive
raising the procurement request the state of material requirement transitions to
Procurement Requisition. Now the event of the Purchase Officer raising an enquiry
on the prospective vendors transitions the state to Enquiry.
Statecharts are used more to depict the design of the proposed system than in
capturing the requirements. All, the same, statecharts are definitely useful in cap-
turing the requirements especially the transition of the state of the entities.
13.5.5 Activity Diagrams
Activity diagrams model the procedural flow of actions that are part of a use case
or a set of use cases. Activity diagrams are normally used to depict the sequence of
execution in a system. Activity diagrams use similar notation as statecharts.
A sample activity diagram is depicted in Fig. 13.14 for the procurement system
in a simplified manner.