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Requirements Management with Use Cases
Module 6: Define the System
Requirements Management with Use Cases
Module 6: Define the System
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 2
Objectives: Define the System
Explain the purpose of a Vision document List the components of a Vision document Write a draft of the Vision Write a product position statement
Identify stakeholders and users Identify stakeholder/user needs Document product features Identify constraints
Develop and describe a use-case model Write a step-by-step outline
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 3
Where Are We in the Requirements Discipline?
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 4
Define the System: Activities and Artifacts
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 5
Organizing Project Artifacts
Develop or adopt standard templates Record your standards in QA Plan Benefits of standardization:
Leverages the work of others Quicker start, avoid reinventing the wheel Make sure things don’t fall through the cracks Everyone knows where to look for information Documents appear familiar and not intimidating Documents are easier to read
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 6
Specifications: Focus on Vision
+ Features
SoftwareRequirements
StakeholderNeeds
Vision Document
User Documentation Specifications
Design Specifications
StakeholderRequests
StakeholderRequests
SupplementarySpecificationUse-Case Model
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 7
System-level document that describes the “Whats” and “Whys” of the product or application
Focus User needs Goals and objectives Target markets User environments and platforms Product features
VisionDocument
Vision Document
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 8
Roles of the Vision Document
Communicate between management, marketing, and the project team
Provide for initial customer feedback Foster general understanding of the product Establish scope and priority of high-level features Record future features and ideas
A document that gets “all parties working from the same book.”
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 9
Vision Document Components
1. Introduction2. Positioning3. Stakeholder and User Descriptions 4. Product Overview5. Product Features6. Constraints 7. Quality Ranges8. Precedence and Priority9. Other Product Requirements10.Documentation Requirements11.Appendix 1 - Feature Attributes
TP4: Vision Document Template
- agree on the problem, capture vocabulary
- problem statementidentify
stakeholders/actors
- brainstorm features
- define boundaries
- identify constraints
- develop RM plan
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 10
Product Position Statement
Communicates intent and importance
Moore ‘91
Hint: Use Problem (analysis) Statement as a starting point!
For (target customer)
Who (statement of the need or opportunity)
The (product name)
Is a (product category)
That (statement of key benefits - that is - compelling reason to buy)
Unlike (primary competitive alternative)
Ourproduct (statement of primary differentiation)
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 11
Product Features
An externally observable service by which the system directly fulfills a stakeholder need
Examples: The Defect Tracking System will provide
trending information to help the project manager assess project status.
The ATM must allow a customer to transfer funds between accounts.
The graphical user interface will provide context-sensitive help.
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 12
Exercise 6.1: Create a Vision Document
Develop a vision for the class project Write a product position statement List identified stakeholders List identified users Summarize key stakeholder/user needs List the features for the class project List project constraints
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 13
Specifications: Focus on Use-Case Model
User Documentation Specifications
Design Specifications
StakeholderRequests
SupplementarySpecificationUse-Case Model
+ Features
SoftwareRequirements
StakeholderNeeds
StakeholderRequests
Vision Document
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 14
Use-Case-Model Survey: Template Use-Case-Model Survey
Gives a complete functional overview of the model
Shows a system’s intended functions and environment
May serve as a contract between the customer and the developers
Is input to activities in analysis, design, and test
Use-Case-Model Survey
1. IntroductionPurpose of the system
2. Survey DescriptionOverview of the use-case model
3. Use-Case-Model Hierarchy
ActorsName and brief description of each actor and its relationships
Use CasesName and brief description of each use case and its relationships
4. Use-Case DiagramsA list of all actorsA list of all use cases
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 15
RU e-st
QuoteSystem
TradingCustomer
AnotherActor
Use Case 3
Get Quote
Another Use Case
AnotherActor
Use Cases Show User Needs
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 16
Exercise 6.2: Describe the Use-Case Model
Review actors (Ex. 4.1) Identify use cases Identify communicates-associations Create a use-case diagram
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 17
Sample Use Case Diagram: RU e-st System
News System
TradingCustomer
Market Trading System
RU e-st Support
Review Account
Execute Trade
Apply for Trading Account
DistributeNews
Manage Portfolio
Get Quote
Quote System
Clock
RUCS4: Use-Case Model Survey
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 18
The Top 10 Use-Case Pitfalls
1. The system boundary is undefined or inconstant.2. The use cases are written from the system's (not the actors')
point of view.3. The actor names are inconsistent.4. There are too many use cases.5. The actor-to-use case relationships resemble a spider's
web.6. The use-case specifications are too long.7. The use-case specifications are confusing.8. The use case doesn't correctly describe functional
entitlement.9. The customer doesn't understand the use cases.10. The use cases are never finished.
...
From Lilly, S., Use Case Pitfalls: Top 10 Problems from Real Projects Using Use Cases,
Proceedings of TOOLS USA '99, IEEE Computer Society, 1999.
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 19
Packages: Grouping the Use-Case ModelThe Use-Case Model
Use-Case Packages
Top-Level Package
Use CasesActors Use-Case Packages
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 20
Avoid Functional Decomposition
Symptoms Very small use cases Too many use cases Uses cases with no
result of value Names with low-level
operations • “Operation” + “object” • “Function” + “data” • Example: “Insert Card”
Difficulty understanding the overall model
Corrective Actions Search for larger
context“Why are you inserting card?”
Put yourself in user’s role“What does the user want to achieve?”
“Whose goal does this use case satisfy?”
“What value does this use case add?”
“What is the story behind this use case?”
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 21
Brief descriptionBasic Flow 1. First step 2. Second step 3. Third stepA1 Alternative flow 1A2 Alternative flow 2 A3 Alternative flow 3
Use case name
Use-Case Outline
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 22
Step-by-Step Outline: Get Quote
Basic Flow1. Customer logs on2. Customer selects ‘Get Quote’ function3. Customer selects stock trading symbol4. Get desired quote from Quote System5. Display quote6. Customer gets other quotes7. Customer logs off
Alternative FlowsA1. Unidentified Trading Customer A2. Quote System Unavailable A3. Quit
What other alternatives can you think of?
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 23
Brief descriptionBasic Flow 1. First step 2. Second step 3. Third stepA1 Alternative flow 1A2 Alternative flow 2 A3 Alternative flow 3
Use case name
Exercise 6.3: Write a Step-by-Step Outline
Create a brief description of the use case Create step-by-step outline of flow of events
Requirements Management with Use CasesCopyright © 1998-2001 Rational Software, all rights reserved 24
Review: Define the System
1. What is the purpose of a Vision document? 2. What are the components of a Vision document?3. What is in the product position statement?4. What is a product feature? 5. Which properties of actors and use cases are
specified in the Use-Case-Model Survey?6. What are some symptoms of functional
decomposition? 7. What is included in a step-by-step outline?