Step 3 to Step 4
Step 3: Creating an Initial Use Case Diagram
Figure 4 – An Initial Use Case Model
In a large software project, we usually need to organize the use cases into packages, and sometimes a hierarchical structure of packages may be needed for very large scale projects. A package is a place holder which can contain any UML elements, including packages themselves. By organizing the use cases into packages, the use case model can be managed more easily. In the case study, we divided the use cases into three packages. Each package contains a set of use cases for handling a certain type of business activity.
Use Case Modeling – Step 4: Describing the Use Case
We need to briefly describe each of the use cases with a short paragraph. The brief description will be further expanded and elaborated on when the use case is analyzed. The following figures give a brief description of the Schedule Delivery use case and the Check Order Status use case.
Use Case:
Schedule Delivery
Use Case ID:
UC-300
Actor:
Order Processing Clerk
Description:
The Order Processing Clerk selects an order from the list of filled sales orders. The system displays the sales order details, and the member’s telephone number and address are displayed. The Order Processing Clerk enters the delivery date and time after talking with the member over the phone. The system records the delivery date and time in a dispatch request to the delivery team.
Table 2 – An Initial Use Case Description of the Schedule Delivery Use Case
Figure 5 – Use Case Description of Schedule Delivery
Use Case:
Check Order Status
Use Case ID:
UC-400
Actor:
Customer Service Assistant
Description:
The Customer Service Assistant enters the ID of the member. The Customer Service Assistant selects a sales order of the member. The system displays the status of the sales order.
Table 3 – Brief Description of the Check Order Status Use Case
Figure 6 – Use Case Description of Check Order Status
Identifying/Refining Candidate Business (Domain) Classes
Having prepared a brief description for each of the use cases, we should try to identify the classes of the system. The identified classes will then be used as part of the vocabulary for writing the expanded use case descriptions.
It is important to note that identification of objects and classes is a continuous process throughout the whole system development life cycle; the class model will be iteratively refined in each step of the system development life cycle.
During the use case analysis process, classes can be identified by performing a textual analysis on the brief use case descriptions. The nouns and noun phrases in the use case descriptions are highlighted and evaluated for possible inclusion as a candidate class. The results of the analysis are a set of candidate classes with their descriptions. An initial class diagram is drawn to show the static relationships between the classes. If a domain analysis has been performed to develop a domain class model, the results of this step will be combined with the domain class model to produce the initial class model. This will be elaborated on in the domain analysis chapter.