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Discovering Use Cases

This text explores the project process, including the inception, elaboration, construction, and transition phases. It discusses important questions to ask during inception, development artifacts, dealing with uncertainty, and digesting the problem through specifications. It also provides an event table and an example scenario for an address book project.

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Discovering Use Cases

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  1. Discovering Use Cases

  2. The Project Process • Inception - initial planning • Elaboration - refining the design • Construction - building the system • Transition - installation support

  3. Inception • Ask important questions such as • What is the system going to do? • What is the business case for the system? • Are we better off buying a system off the shelf? • Development Artefacts • Project specification • Ethical review • Event tables • Initial use case diagrams + descriptions • Class diagram • Early prototype – a “smoke and mirrors” model of how the system will work • Testing – test plans – test framework – usability testing

  4. Dealing with Uncertainty • Project development is not a nice clean and tidy process • Uncertainty and Proofs of concept • Should the main screen be blue or green? • Will the language I am using work on that version of the operating system? • How do I process this list of data to format it in a specific way? • I am really not very clear on what the user wants with this single requirement? • Is it possible to connect this system to Oracle rather than SQL server?

  5. Digesting the Problem – The Specification As a self employed computing consultant you encounter a large number of people whilst involved in your networking activities. One consequence of these activities is that you accumulate a huge number of business cards/flyers. These documents contain a large quantity of useful information that needs to be input into suitable database system.

  6. Role Play the Scenario • Who, what, when, where and why? • (If you are not clear on any of these points then you must return to the client and find out.)

  7. Refined Specification The consultant sits at their desk with a stack of business cards and flyers. They pick up a business card and start to input the details into system. The first field they enter is the name of the company. While doing this the system looks up the company name to see if it is already on the system. The next field the user enters is the name of the contact. Whilst dong this, the list of contacts for that company is displayed such that if the contact is already on the system the user may move onto another business card. At this point the user should have the opportunity to update the details on the system should they note that some aspect has change e.g. email address.

  8. The Event Table • Probably the most useful tools for digesting the problem • Informs your use cases • Informs your class diagram • Don’t get hung up on it being right • Better to add more events and discount them later • Understanding will still be fuzzy at this stage of the game

  9. Address Book Event Table

  10. Identify Candidate Events from the Specification The consultant sits at their desk with a stack of business cards and flyers. They pick up a business card and start to input the details into system. The first field they enter is the name of the company. While doing this the system looks up the company name to see if it is already on the system. The next field the user enters is the name of the contact. Whilst dong this, the list of contacts for that company is displayed such that if the contact is already on the system the user may move onto another business card. At this point the user should have the opportunity to update the details on the system should they note that some aspect has change e.g. email address.

  11. Some Filtering Required • Not events but still contain important information about the system • “consultant sits at desk” • “pick up a business card” • Are these the same thing? • “input the details” • “enter the company name” • “enter the name of the contact”

  12. Identify the Verbs in the Event Table

  13. This Informs the Selection of Use Cases

  14. The Subject Column Identifies the Actors

  15. Create Use Case Descriptions

  16. Exercise Extended Specification On the module web site you now have the extended specification for the project bank. Working in teams select one of the features from the specification and brain storm the following.  • Flesh out a detailed scenario • Event table (Subject – verb – object – response) • What candidate actors / use cases do you come up with?

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