From Use case to User Story

FROM USE CASE to USER STORIES

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

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

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

2. Scope Your Use Cases Frame each use case with: triggering events event responses

2. Scope Your Use Cases 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”

2. Scope Your Use Cases 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 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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