use cases
Download
Skip this Video
Download Presentation
Use Cases

Loading in 2 Seconds...

play fullscreen
1 / 26

Use Cases - PowerPoint PPT Presentation


  • 130 Views
  • Uploaded on

Use Cases. High-level system description. System description. Typical description has two parts data operations on that data Three possible descriptions requirements specification design. Many notations. UML Use cases Class diagram State diagram Hamlet and Maybee

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Use Cases' - gyda


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
use cases

Use Cases

High-level system description

system description
System description
  • Typical description has two parts
    • data
    • operations on that data
  • Three possible descriptions
    • requirements
    • specification
    • design

CS427

many notations
Many notations
  • UML
    • Use cases
    • Class diagram
    • State diagram
  • Hamlet and Maybee
    • Finite state machine, Data flow diagram
    • Prolog
    • Pseudocode

CS427

many purposes
Many purposes
  • Communicate to
    • User
    • Developers
    • Boss
  • Complete - lots of detail
  • Easy to read - less detail

CS427

writing effective use cases
Writing Effective Use Cases
  • Alistair Cockburn
  • Know the inside cover, front and back
  • www.usecases.org
    • papers
    • discussion boards

CS427

use case diagram
Use case diagram
  • Shows actors and use cases
  • Shows system scope and boundaries
  • Not a description of use cases
  • Like a context diagram

CS427

scd for claims processing
SCD for Claims Processing

Claim adjudicator

Data entry

Data repair

Electronic claim

Claims Processing

System

Mainframe

Fax

Postal System

Postal System

CS427

use cases1
Use Cases
  • Text - a form of writing.
  • Describes the system’s behavior as it responds to a request from an actor.
  • Many kinds of use cases
    • Brief / detailed
    • Requirement / specification / design

CS427

use cases2
Use cases
  • Describe the sequence of events that happen when the system responds to a request
    • Can describe alternatives
    • Can describe errors

CS427

use cases are text
Use cases are text
  • Use cases should be easy to read
    • keep them short
    • tell a story
    • write full sentences with active verb phrases
    • make the actors visible in each sentence

CS427

many ways of writing use cases
Many ways of writing use cases
  • User stories
  • Actor-goal list
  • Use case briefs
  • Casual use cases
  • “Fully dressed” use cases

CS427

actor goal list
Actor-Goal List

Actor Task-level goal Priority

Provider Submit paper claim 1

Provider Submit fax claim 2

Provider Submit electronic claim 3

Adjud. Adjudicate problem 2

CS427

use case briefs
Use case briefs

Brief

Submit claim on paper, which is converted into electronic form, and either paid or sent for adjudication

Submit claim by fax, which is processed by OCR and either paid or sent for adjudication.

Decide whether a questionable claim should be paid by the mainframe payment system or rejected

Actor

Provider

Provider

Adjucator

Goal

Submit paper claim

Submit fax claim

Adjudicate failed claim

CS427

brief casual version of submit fax claim
Brief (casual) version of Submit Fax Claim

The Provider submits a claim by fax. The claim processing system will log the image to optical disk, apply form dropout, deskewing, despeckling, and then process it using OCR. Knowledge workers will repair any fields that seem to be in error. The claim will then either be paid (using existing mainframe processing system) or sent to adjudication.

CS427

detailed fully dressed version of submit fax claim
Detailed (fully dressed) version of Submit Fax Claim

Primary Actor: Provider

Goal in context: Pay legitimate claims while rejecting bad ones.

Scope: Business - the overall purchasing mechanism, electronic and nonelectronic, as seen by the people in the company.

Level: Summary

Stakeholders and interests:

Provider: Wants to be paid for services rendered.

Company: Wants to cut costs and avoid fraud

Precondition: none

Minimal guarantees: Pay only certified providers, pay only for services that are covered by plan, do not pay if there are obvious mistakes

CS427

main success scenario
Main Success Scenario:

Trigger: Claim submitted by fax

1. Provider: submit claim by fax

2. Claim system: drop forms, deskew, despeckle, use OCR to convert to electronic form

3. Claim system: check claim to make sure it is legal

4. Mainframe payment system: pay claim

Extensions:

2a. Some fields have low confidence: Knowledge worker corrects

3a. Claim is not valid: send to adjudication

CS427

use cases and requirements
Use Cases and Requirements
  • An important part of requirements
  • Help requirement traceability
  • Help manage requirements

CS427

requirements
Requirements
  • Use cases
  • Stakeholders - people who care
  • Business case - cost of project, time to complete project
  • Interfaces with outside systems
  • Technology requirements
  • Ease of use, ease of maintenance, throughput and response time

CS427

traceability
Traceability
  • Traceability - the ability to trace the effect of a requirement and determine who caused it
    • Why do we have this requirement? Who wrote it?
    • How is this requirement met?
    • What requirement caused this design?

CS427

manage requirements
Manage requirements
  • Must agree to change in requirements
    • Usually increases price
    • Must be reviewed
  • Make sure each part of design is due to a requirement
  • Analyze problems: what was the root cause of this bug?

CS427

scenarios and use cases
Scenarios and Use Cases
  • Scenario is concrete and detailed
    • names of people
    • $ values, particular dates, particular amounts
  • Scenario is a test case
  • Use Case is a contract, and collects all the scenarios

CS427

goals and use cases
Goals and Use Cases
  • Actor has a goal for the use case
  • System forms subgoals to carry out its responsibility
  • Goals can fail
  • Use case describes a set of ways for carrying out the goal, and several ways of failing

CS427

when use cases don t work
When use cases don’t work
  • Compilers
    • one use case - compile a program
  • Despeckler
    • one use case - remove speckles
  • No interaction
  • Complexity is caused by
    • input format
    • transformation

CS427

summary
Summary
  • Use cases are useful, but not perfect
  • Many ways to write use cases
  • Big projects need big use cases
  • Use the simplest way you can!

CS427

reading
Reading
  • Chapter 8 of Hamlet and Maybee
  • Either chapters 7, 9, and 16 of Kruchten or read about the planning game (the first part of 10, the first part of 11, and 15 of Beck, or maybe http://c2.com/cgi/wiki?PlanningGame)

CS427

ad