Use-Case Diagram. Contents. Introduction. 1. Introduction. User-Centred Design (UCD) Users Requirements

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1 Contents Use-Case Diagram MIT, Walailak University by Dr.Wichian Chutimaskul Introduction Business Model using Activity Diagram Domain Analysis using Use-Case Description Documenting Requirements using Use-Case Diagram Create Use-Case Description & Diagram Use-Case Consideration Dennis: Copyright 2009 John Wiley & Sons, Inc Introduction Users Requirements Need to understand how the organization operates at present What are the problems with the current system (AS-IS)? What are the requirements users have of a new system (TO-BE) that are not in the current system? User-Centred Design (UCD) Problem: failed to involve users adequately in the development process Ignore users Don t have functions users needed It is hard to understand It is time consuming to use User-Centred Design: to describe approaches to system development that focus on the needs of users to ensure that extensive and expensive modifications are not needed Lethbridge 3 Lethbridge 4

2 IS Development Project Track Record Documenting Requirements Activity diagram to model tasks (i.e. business process) to describe functions of a system represented by a use case to describe the logic of an operation Use-case diagram to document functional requirements canceled before completion Over budget, late, or without needed features Source: The Standish Group International, Inc., Chaos: A Recipe for Success Ivar Jacobson 1990 Scenario Document behavior of the system from users point of view Whitten 5 6 Activity Diagram Requirements Analyst 2. Activity Diagram Define how activities are coordinated Project Initiation Document Candidate Requirements Elicit requirements Select requirements Develop use cases Glossary Requirements List Use Case Model Notation 1 Activity rectangle with rounded ends meaningful name (verb + noun) 2 Transition arrows with open arrowheads Add a New Client Assign Staff Contact Bennett 7 Lethbridge 8

3 Notation of Activity Diagram Notation of Activity Diagram 3 Start state/marker black circle 4 Decision point diamond 5 Guard condition in square brackets 6 Final state/ stop marker black circle in white circle Add a New Client Assign Staff Contact Add New Campaign [no campaign to add] [campaign to add] 7 Alternative notation for branching: alternative transitions are shown leaving the activity with guard conditions Add a New Client Assign Staff Contact Add New Campaign [no campaign to add] [campaign to add] Lethbridge 9 Lethbridge 10 Notation of Activity Diagram Notation of Activity Diagram 8 Object flows dashed arrow 9 Objects rectangle with name of object underlined optionally shows the state of the object in square brackets :Campaign [Active] :Campaign [Completed] Record completion of a campaign 10 Swimlanes vertical columns labeled with the person, organisation or department responsible for the activities in that column Campaign Manager Record Completion of a campaign Record client payment Accountant Issue invoice Client Pay invoice Human: activity diagram shows workflow Software component: activity diagram shows program control flow Lethbridge 11 Lethbridge 12

4 Drawing Activity Diagram 1 Identify activities 2 Organize the activities in order with transitions 3 Identify any alternative transition and the condition on them 4 Identify any process that is repeated 5 Add swimlanes, if required 6 (option) Add object & object flow Exercise Logic 1 Customer buys goods 2 Send order to sales 3 Request items from inventory 4 Pack items 5 Ship items to customer & billing (parallel) 6 Payment Customer Sales Warehouse Use-Case Description Elements of a Use-Case Description (Template) Describe basic functions of the system What the user can do How the system responds The set of all use-case descriptions specifies the complete functionality of the system A. Overview Information Use-Case Name: Verb+noun ID: Importance Level: Primary Actor: Use-Case Type: (overview-detail/essential-real) Stakeholders and Interests: Brief Description: Trigger: B. Relationships: (Association, Include, Extend, Generalization) C. Flow of Events Normal Flow of Events: Subflows: ******* Alternate/Exceptional Flows: 15 16

5 7 Guidelines for Creating Use-Case Description 1 Write each step in SVDPI form subject-verb-direct object-preposition-indirect object 2 Clarify initiator and receivers of action 3 Write from independent observer perspective 4 Write at same level of abstraction 5 Ensure a sensible set of steps (betw. actor & system) 6 Apply KISS (keep it simple stupid) principle liberally 7 Write repeating instructions after the set of steps to be repeated. Exercise How would you make requirements gathering (interviews, questionnaires, observation, and document analysis) more effective by knowing that eventually you will be creating use-case description and diagram? Use-Case Diagram Summarize all the use-cases for a system being modeled together in one picture Purpose: documenting requirements Document the functionality of the system from the users perspective Document the scope of the system Document the interaction between the users and the system using supporting use-case description Actor - Use-Case - Association - Boundary Actor users system organization drawn as stick people with a name communicate with particular use-case(s) Use-case main function drawn as an ellipse with a name in each ellipse the name is usually an active verb and a noun phrase Association connect use-cases and actor Boundary Bennett 19 Bennett 20

6 Syntax of Use-Case Diagram Syntax of Use-Case Diagram Use-Case Diagram for Appointment System Use-Case Diagram with Specialized Actor Use case association Actor System or subsystem boundary 23 24

7 Use-Case Type Basic Use-Case Extension Use-Case Abstract Use-Case (for reuse) An abstract use case is a use case that is never directly instantiated, but rather exits for other use cases to reuse Basic Abstract Extension Use-Case Relationship Association An association between an actor and a use-case Extend-relationship: «extend» Used to make optional interactions explicit or to handle exceptional cases List all steps from the beginning of a use case to the end Include- (abs) relationship: «include» or «use» Allow one to express commonality between several different use cases to avoid repeating details in multiple use cases Extend and Include Relationships (1) Extend and Include Relationships (2) Extend loan <<include>> Library IS Borrower Borrow copy of book <<include>> Check for reservation Return copy of book <<extend>> Calculate Fine 27 28

8 Exercise Which of the following use-case diagram is legal? Draw a use-case diagram showing the relationship among the following. The exit car park requires to pay cash or debit card. There is also an abnormal case of exiting car park without initially entering enough money. A «use» «extend» C «use» «extend» B D «use» «extend» «use» «extend» Major Steps in Writing Use-Case a. Identify the major use-case b. Expand the major use-case c. Confirm the major use-case d. Create the use-case diagram a) Identifying the Major Use-Cases 1 Identify the system s boundaries 2 List the primary actors 3 List the goals of each primary actor 4 Identify and write the major use-cases 5 Carefully review use-cases # Actor Use Case Description 31 32

9 b) Expand the Major Use-Cases 6 Choose one major use-case to expand 7 Fill in details on the use-case template 8 Fill in the steps of the normal flow of events 9 Normalize the size of each step 10 Describe alternate or exceptional flows *** 11 Simplify and organize as necessary c) Confirm the Major Use Cases 12 Review the current set Consider semantics and syntax Helpful to involve the users 13 Iterate the entire set of steps until all use cases are defined d) Create the Use-Case Diagram 1 Start with system boundary 2 Place elements (use-cases) in order to be easy to read 3 Place actors on the diagram 4 Conclude by connecting actors to use cases by lines 6. Use-Case Consideration Use-Case Packaging Buying Buy Goods Customer <<extends>> Out of Stock <<extends>> Return Goods <<include>> Sell Goods to Company <<include>> Handle returned goods Selling Common 35 Peter Swin 36

10 Consideration A UC diagram is not a specification It is a road map for reading the flows of events A UC diagram is not a software design It is used to structure a textual description. A UC should not provide details of UI interaction It is a sequence of actions that yields a measurable value to the actor How Precise should Use-case be? Understandable by users Don t use use-cases to functionally decompose system Don t use use-cases to formally specify the system Disciplined and consistent in terms used Larry Constantine Model: OO Structured Summary Function/Task Use-case diagram Context diagram Activity diagram Structure Behavior Class diagram Interaction diagram Sequence diagram Communication / Collaboration diagram ERD DFD Use-case description is the basis for further analysis and design. They are created based on 7 guidelines and 13 steps. Use-case diagram presents a graphical overview of the main functionality of a system. State diagram Activity diagram Business process Use case Operation Further Read:

11 Question and Answer Systems Analysis and Design with UML: An Object-Oriented Approach, 3rd Edition, Dennis, B.H. Wixon and D. Tegarden, Wiley 2009: Chapter 5 41 T/F Question 1. A(n) is an informal way of representing how a business system interacts with its environment. 2. Each use-case describes one function in which users interact with the system. 3. The association relationship in use cases allows use cases to support the concept of inheritance. 4. An alternate or exceptional flow in a use case documents the decomposition of the normal flow of events. 5. An informal way of representing how a business system interacts with its environment is termed a use-case. 42 Team Assignment Draw an activity diagram (business process) of your project study Complete the functional analysis (user-case diagram) of your project study Submission Date: two days before the class Time: 1 p.m. to: wichian@sit.kmutt.ac.th cc: your team members Subject: OOSAD# (x) (where # is your team number & x is any text. Send: Only one.doc file (including the old work) Case-Study: ECO Storage Depot 1. The ECO Storage Depot operates in accordance with the Environmental Protection Agency (EPA) regulations controlling the storage of environmentally damaging chemicals. The ECO depot is licensed only to store drums of chemicals classified as EPA hazard types 1, 2 or The drums are stored in special storage buildings; in the depot there are also buildings that house scientific and administrative staff. Each storage building is licensed to hold a maximum number of drums. Furthermore the EPA requires that types 1 and 2 must not be stored together in the same building; however, type 3 may be stored with either types 1 or 2. If either of these regulations is violated, then the EPA will close the depot as unsafe, pending emergency action. 3. Management has decided to install a computerized system to manage and control the depot. It is of paramount concern that the system never allows the depot to become unsafe

12 ECO Storage Depot 4. ECO management is concerned about avoiding litigation from employees or the local council. They have introduced a company regulation that requires the depot manager to be able to monitor the state of the depot and to always be able to check if the depot is in a vulnerable state. The regulation states that the depot is vulnerable if any of two neighboring buildings contain the maximum permitted number of drums. 5. When a truck arrives at the loading bay, the clerk enters the manifest accompanying the load and checks the drums one at a time. As each drum is checked in, it is allocated an identifier. Once all the drums have been checked in, any discrepancy between the checked load and the manifest are notified to the loading bay clerk. The system then produces a drum-to-building allocation list that specifies where each drum to be stores. The loading bay clerk is notified of any drum that must be returned to the truck through lack of space. 6. Drum collections are initiated by the loading bay clerk inputting an order manifest for the number and type of drums required. The system identifies the drums that are to be retrieved from storage buildings. A manifest for the order is sent to the loading bay clerk. 7. Because there is only one loading bay, it must be empty before a delivery or collection can begin. It is the clerk s responsibility to notify the system when the bay is empty. Answer Exercise: Create Use-Case Diagram of this system