Use Cases UML Use Cases What are Use

Use Cases UML

Use Cases

What are Use Cases? A statement of the functionality users expect and need, organized by functional units Different from user stories because they are from the software’s perspective In Ø Functional units are any natural division Ø Relationships between user types and use cases Ø User activities, decisions, and objects involved terms of user types: classifications that the system recognizes

Use Case Usage determining features (requirements) basis for communicating with clients generating test cases

For requirements sprint Concept User stories Personas Full set of use cases and requirements

For each sprint Select the use case(s) that you will support Identify the requirements they engender For those cases, Functional spec: what it does Test cases: how I know it does it Design doc: how it does it User manual: how the user knows what to do Code: does it

Documenting Use Cases Simple text description UML diagrams

Documenting Use Cases We will use simple text description Examples from prior years Butterfly Lab Foreign Language Resource Center

UML: Unified Modeling Language A BRIEF DETOUR

What is UML? software blueprint language: common vocabulary for analysts, designers, and programmers not for the customer applicable to object-oriented problem solving begins with the construction of a models consist of objects interact by sending messages attributes: things they know behaviors or operations: things they can do state Also used for business processes Contradicts “not for the customer”

Modeling (Will return to it) Based on abstraction looking only at relevant information hiding details Multiple views as orthogonal as possible each view has information that is unique appears in other views common information is consistent

Modeling Languages and Processes Language: syntax usually graphical used to express design Process: steps to take to create a design Many processes, not a lot of agreement General consensus has built around UML as a language

UML History Three well received models in early 90 s Grady Booch (Rational), Object Oriented Analysis and Design Jim Rumbaugh (GE), Object Modeling Technique Ivar Jacobson (Ericsson), Object Oriented Software Engineering By ’ 95, all three “amigos” were working for Rational (acquired by IBM in 2002) OMG adopted UML in ’ 97 (www. uml. org) Version 2. 0 completed in 2004

Why Study UML? software engineering useful tool cultural literacy natural model for design lots of good tools Rational Some code generates C++ and Java code people expect tools to generate good for prototyping good for development? Would this be good or bad?

What UML Is and Isn’t Syntax only Standardized Language and tool independent Generic enough to be Extendable through “stereotypes” Usable in lots of environments And leaving you lots of space to misuse it New symbols built up from basic ones Used to develop a business process model Not a process There is a companion one—Unified Process

Good Reference Fowler, UML Distilled, Addison-Wesley 3 rd edition, 2004, covers 2. 0 Short Good summary charts on inside covers

Diagram Types Diagram Use case Class Object Sequence Collaboration Statechart Activity Component Deployment Static/Dynamic Static Phase Requirements Design Dynamic Static Design Code Deploy

UML Views: Diagram Types Use Case – outside view (scenarios) Class – classes and relationships among them Object – instances instead of classes Sequence – how & when objects interact through messages Collaboration – how objects interact through roles Statechart – object behaviors as reflected through states Activity – flow diagram of classes & interactions Component – analogous to class but for code module Deployment – physical configuration of system nodes

Pitfalls of UML can feel like you’ve accomplished more than design because there are tools and artifacts need to know when to stop designing variant of analysis paralysis

Symptoms of UML Fever (Bell, Queue, March 2005) expecting more from UML than it was ever intended to do (performance, fault tolerance) taking UML to too detailed a level UML products become most of the milestones UML syntax discussions dominate design brainstorming sessions “if it can’t be described in UML, it’s not relevant” UML designed without user input

Back to Use Cases

Use Case Diagram Defines the outside view Elements Actors (stick figures): anything outside the system that interacts with it Use cases (ovals): procedures by which the actor interacts with the system Solid lines: indicate how actors interact

Use Case Extensions Dotted lines: dependencies between procedures Includes (subroutine) Extends (variation)

Example of Use Case (customer name)

A UML Gallery

Class Diagrams Static structure of the system. What interacts, but not what happens.

Object Diagrams object diagram: instantiates class diagram

Sequence Diagram

Collaboration Diagram Alternative to sequence diagram Focus on object roles instead of the times that messages are sent

Statechart Diagram Often used in real-time embedded systems Shows the order in which incoming calls normally occur

Activity Diagram General purpose flowchart

And… Component Diagram Deployment Diagram