CH3: Use Cases
Event Decomp: Steps 1 & 2
1. Consider external events in system that require a response from the system by using checklist 2. For each external event, identify and name the use case that the system requires
CRUD Technique
1. Create, read/report, Update, Delete (archive) 2. Validate, refine or cross check use cases 3. Often introduced in database context 4. Not for identifying use cases
Event Decomp: Benefits
1. Events broader than user goal 2. Decompose right level of analysis (elementary business process) 3. Perfect technology assumption: make sure functions that support user work are identified
External Event Checklist
1. External agent/actor wants something resulting in a transaction 2. External agent/actor wants some info 3. External data changed and needs to be updated 4. Mgmt wants some info
Use Case: Step 1 & 2
1. Identify all stakeholders and users who would benefit by seeing a use case diagram 2. Determine what each stakeholder or user needs to review in a UCD, subsystem, type of user
CRUD: Steps 1 & 2
1. Identify all the data entities or domain classes involved in new system 2. For each type of data, verify that use case has been identified that creates a new instance etc
User Goal Technique: Steps 1 & 2
1. Identify all the potential users for the new system 2. Classify the potential users in terms of their functional role
Temporal Event Checklist
1. Internal outputs need at points in time (mgmt reports, operational reports, internal statements and documents) 2. External outputs needed at point of time
Event Decomposition Technique
1. More comprehensive and complete 2. Identify events that occur to which system must respond 3. For each event, name a use case (verb noun)
Event Decomp: Steps 3 & 4
3. Consider temporal events requiring a response from system by using checklist 4. For each temporal event, identify and name the use case that system requires and establish the point in time that will trigger
Use Case: Step 3 & 4
3. For each potential communication need, select use cases and actors to show and draw diagram 4. Carefully name each diagram and note how and when the diagram should be to review use cases w stakeholders and users
User Goal Technique: Steps 3 & 4
3. Further classify potential users by org. level (operational, mgmt) 4. For each type of user, interview them to find a list of specific goals they will have when using the new system
CRUD: Steps 3 & 4
3. If a needed use case has been overlooked, add a new use case and then identify the stakeholders 4. W integrated apps, make sure it is clear which app is responsible for adding and maintaining data/which system merely uses the data
Event Decomp: Steps 5 & 6
5. Consider state events that system might respond to, esp if it is a real time system 6. For each state event, identify and name the use case that the system requires and then define state change
User Goal Technique: Steps 5 & 6
5. Create a list of preliminary use cases organized by type of user 6. Look for duplicates with similar use case names and resolve inconcsistencies
User Goal Technique: Steps 7 & 8
7. Identify where different types of users need the same use cases 8. Review the completed list with each type of user and then w interested stakeholders
<<includes>> relationship
A relationship between use cases in which one use case is stereotypically included within the other use case
Use Case
An activity that the system performs, usually in response to a request by a user- define functional requirements
Temporal Event
An event that occurs as a result of reaching a point in time
External Event
An event that occurs outside the system, usually initiated by an external agent or actor
State Event
An event that occurs when something happens inside the system that triggers some process
Brief Use Case Description
An often one-sentance description that provides a quick overview of a use case
Functional Decomposition
Decomposing the system into a set of use cases
User Goal Technique
Most common in the industry for identifying use cases- identify all potential categories of users in system, interview to describe what it helps them with
Event
Something that occurs at a specific time and place, can be described, and should be remembered by the system
Elementary Business Process (EBP)s
THe most fundamental tasks in a business process, which leaves the system and data in a quiescent state, usually performed by one person in response to a business event
Perfect Technology Assumption
The assumption that a system runs under perfect operating and technological conditions
Automation Boundary
The boundary between the computerized portion of the app and the users who operate the app
Use Case Diagram
UML model used to graphically show use cases and their relationships to actors
UML
Unified Modeling Language, the standard for diagrams and terminology for developing info systems
Event Decomp: Step 7
When events and use cases are defined, check to see if they are required by using the perfect tech assumption. Do not include events that involve such system controls: login, logout, backup.
