From Use case to User Story

FROM USE CASE to USER STORIES

Use Case Introduction

Why are Requirements important
1/3 budget to correct errors originate from requirements
Defining requirements is crucial to all project stakeholders
Many techniques and models available
USE CASE MODEL

Why should you be interested ?
IDEO Story:
Biker water bottle – heart valve
Multidiscipline cooperation

What are Requirements
It covers :
Functional requirements
User requirements
Nonfunctional requirements
Quality attributes: performance, security, archiving, database
defined operational capabilities business needs satisfy

Software Requirements
Three perspectives:
Business level
User level
Technical level

Business Level
Define the vision
Build the right software
Define project stakeholders:
including direct users (actors)

User Level
Use cases :
“ voice of customers”
consists of :
interaction
has name
step-by-step
exception conditions
variant paths

Technical Level
Technical requirements:
Functional requirements based on user requirements
Nonfunctional requirements

Use Case Concepts and Definitions

Use Case
Describes how the system should respond under various conditions to a request from one of the stakeholders to deliver a specific goal .
stakeholder = primary actor

Use Case
The use case is primarily done in the form of a scenario that describes a sequence of steps .
Each use case captures a ‘contract’ for the behavior of the System under Discussion (SuD) to deliver a single goal .

Actors
Anyone or anything with behavior.
Generally is a role (rather than a specific person, job title or a thing)
Not every stakeholder will show up
Important to discover these ‘hidden’ actors

Primary Actor
Stakeholder that interacts with the SuD to achieve a specific goal

Supporting Actor
An (external) actor that needs to provide a service to the SuD
A primary actor for one use case can become a supporting actor for another

Scenario
sequence of steps
fulfill a goal

Scenario
Must be easy to read
Avoid more than nine steps
Use active voice
Stating who or what is doing what
Approver approve a task
The approver open My Tasks
The approver choose a task
The approver approves the task
The system returns the approver to My Tasks list

Main Success Scenario
Everything goes as planned
Happy Path

Extensions
Exceptions that requires a deviation from the planned scenario
Exceptions documented as extension

Extensions
Approver approve a task
Main Success Scenario
The approver open My Tasks
The approver choose a task
The approver approves the task
The system returns the approver to My Tasks list
Extensions
3a The task has been approved by another approver
3a1 The system returns error message to the approver
3b The approver decides to postpone the approval process
3b1 The approver click the ‘Back’ button
3b2 The system returns the approver to My Tasks list

Use Case Properties
Design Scope
Stakeholder
Primary Actor
Description
Level
Pre-conditions
Post-conditions
Trigger

Design Scope
Definition of the boundary of the System Under Discussion (SuD)
Set of systems that will be designed

Design Scope
A business use case has enterprise as its scope and focus on business flow
A system use case has computer system as its scope and focus on how actors communicate with the system
A component use case has subsystem or component of the system as its scope

Use Case Level
Summary (cloud level or kite level)
outlines the context of a set of User Goal use cases
User Goal (sea level)
addresses “Can the primary actor go away happily after the use case finished ?”
Subfunction (under water level)
created to move out an isolated part of a scenario to a separate use case
source : Alistair Cockburn, Writing Effective Use Cases

Use Case level
Summary
User Goal
Subfunction

Stakeholder & Primary Actor
Stakeholder:
someone / something that has an interest in the goal of the use case delivers
Primary Actor:
the stakeholder who or which initiates the use case to achieve a goal

Description
Brief description of the goal the use case supposed to deliver

Preconditions
conditions that must hold true before the scenario of the use case starts
will not be checked again after that

Post conditions
Minimal Guarantees
What at least should hold true when the goal is not met
Example:
“ All entered information have been stored.”
Success Guarantees
What must have been achieved at the end of the main success scenario or any alternate route.
Example:
“ The task is approved”

Trigger
event or sequence of events that initiate the use case

Use cases Process Flow

Develop in Iterations
Identify all actors and their goals
Use MoSCoW list to define the scope of the project.
Set up Actor-Goal List

MoSCoW List
Must Have : The requirement is essential, key stakeholder needs will not be satisfied if this requirement is not delivered and the timebox will be considered to have failed
Should Have : This is an important requirement but if it is not delivered within the current timebox, there is an acceptable workaround until it is delivered during a subsequent timebox
Could Have : This is a ‘nice to have’ requirement; we have estimated that it is possible to deliver this in the given time but will be one of the requirements de-scoped if we have underestimated
Won't Have : The full name of this category is ‘Would like to have but Won’t Have during this timebox’; requirements in this category will not be delivered within the timebox that the prioritisation applies to

Actor-Goal List L Find unfinished task and reject it Reject unfinished task Support H Receive request and approve it Approve Request Approver H Make change in edit group and send it Submit Change Request Requestor Prio Brief Descriptions Goals Actor

Recipe
Identify the actors
List their goals
Add brief descriptions to the goals
Create an initial use case for each goal
Describe the main success scenario for each use case
Identify the exceptions to the main success scenario and work them out as extension
Validate the use cases
Optimize the use cases

Cheat Sheet
http://www. slingcode .com/ref/ UseCaseQuestions . pdf
by Alistair Cockburn
author of a popular use case book: “Writing Effective Use Cases”, ISBN 0-201-70225-8, ISBN 978-0201702255

Use Case Best Practices

7 Best Practices
Scope the domain
Scope your use cases
Validate use cases
Define the requirements models
Determine the strategy to elicit requirements
Settle on a standard format for your uses cases
Develop a project glossary

1. Scope the Domain
Manage avoidable scope creep
Be flexible on unavoidable market and business condition changing

How to name a Use Case
Well named use cases
enable business customers (or any readers) to easily infer who the actor is
What’s in a name ?

Best practices (1)
action verb + [qualified] object
place order, request product or service
avoid vague verbs, such as do or process
avoid low-level, database oriented verbs, such as create, read, update, delete
The “object” part of the use case name can be a noun, (such as inventory), or a qualified noun (such as in-stock inventory )

Best Practices (2)
make sure the project glossary defines the object
Add each object to the domain model (as a class, entity, or attribute)
Bring forth actors and use cases concurrently and associate them

2. Scope Your Use Cases
A use case
addresses a single actor goal
is not overly complex
avoid partial processes in the business
avoid CRUD (create-read-update-delete)
avoid separate use cases for alternative courses

Frame each use case with:
triggering events
event responses

Different kind of events:
Business Events:
subject + verb + object
for eq: “Customers requests book”
Temporal Events:
time to <verb + object>
for eq: “ Time to generate report”

Context diagram:
simple diagram
system as a single ‘black box’
actors “give” or “get” something to or from the system

3. Validate Use Cases
Questions to validate:
help achieve goals and visions ?
address the problem ?
key differentiator ?
address all stakeholders ?
priority for initial release ?

4. Define the Requirements Model
acts as a blueprint
primary purpose to communicate
discovery process
emphasize on one view
multiple model => separation of concerns

4. Define the Requirements Model
Multiple views:
use cases: behavioral
class diagram: structural
statechart diagram: dynamic (lifecycles)
business rules: control

5.Determine Your Elicitation Strategy
One-on-one or groups interviews
Facilitated workshops
Generate list of scenarios
Reuse existing requirements
Prototype user interface
Observe end users
Focus groups
Market surveys
Regulations and procedures
Customer complaints, help desk logs
Competitive analyses

5. Determine Your Elicitation Strategy
Commercial software: market surveys, on-site visits, facilitated workshops
In-house business system with large user base: review help desk logs, reusing existing requirements, workshops
Smaller user base: facilitated workshops and observation.

6. Settle on Standard Format
use case name only (“verb + [qualified] object”)
use case name and a single-sentence goal statement
use case brief description (2 to 5 sentences)
use case outline (bulleted or numbered list of use case steps, with alternative flows outlined separately or not listed at all)

6. Settle on Standard Format
Use case conversational format (use case header information plus two columns – one for actors and one for system responses – written in a conversational style)
Use case description (a sequential, conversational, or narrative text description that includes normal path, alternative, exceptions and extensions)

7. Develop Glossary
communication gaps between software vs business people
each side has its acronyms and jargon
glossary should be a living, vital part

USE CASE Modeling

Use case Modeling
Use case is a text form
Use case diagram provides an index to use cases

Actor
Someone or something outside the scope of the use case that initiate the use case
May trigger or recipient of the use case

Actor / Use case Associations
relationship between an actor and a use case
actor initiates the use case
use case provides the actor with results

Generalization
To express some high-level functional need of a system
“ a kind of” relationship

Inclusion
Higher-level use cases may call ( includes) lower-level use cases

Extension
An alternate route to the main success scenario.
Extension point: the point it exits the originating use case
Return point: the point at which it returns
Abort Transaction Trigger : any time in Buy Ticket the Car Driver can abort the trans. Main Success Scenario 1. The Ticket Machine returns the coins that have been entered

User Stories Scrum methodology

What is a User Story ?
A concise, written description of a piece of functionality that will be valuable to a user (or owner) of the software

User Story Description
As a [user role] I want to [goal] so I can [reason]
For example:
As a registered user I want to log in so I can access subscriber-only content

How detail should a User Story be ?
Detailed enough
Detailed enough for the team to work from, and further details to be established and clarified at the time of development.

User Stories Summary
User Stories combine written and verbal communications, supported with a picture where possible.
User Stories should describe features that are of value to the user, written in a user’s language.
User Stories detail just enough information and no more.
Details are deferred and captured through collaboration just in time for development.
Test cases should be written before development, when the User Story is written.
User Stories need to be the right size for planning.

Use Case vs User Stories When to use What

Structured Requirements
Goals are achieved through use cases
Use cases are enabled by functional requirements
Functional requirements lead to design and implementation.
Non-functional requirements characterize how functional requirements must work.
Constraints restrict how functional requirements may be implemented
source: Software Requirements, 2 nd Edition, Karl E Wiegers

Documentation Overhead source : http://tynerblain.com

What are the differences ?
Formal use cases require the most effort
Describe all permutations
Informal use cases are pretty much the same - just less formal
Need the right level of detail
Use case briefs have almost no overhead
Same challenges “how much is enough ?”
User stories have the least overhead, and provide the least context.

Level of Details captured source : http://tynerblain.com

Level of Reader expertise source : http://tynerblain.com

References
Ellen Gottesdiener, “Use Cases: Best Practices”, IBM, 6/11/2003
Jan Kettenis, Getting Started With Use Case Modelling, An Oracle White Paper, March 2005
Dan Pilone, UML 2 in A Nutshell, O’Reilly
http://tynerblain.com/blog

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From Use case to User Story

by ckunta on Aug 29, 2009

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From Use case to User Story — Presentation Transcript