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Show 7 Chapter 7: The Object-Oriented Approach to Requirements Systems Analysis and Design in a Changing World, 3rd Edition 7 Learning Objectives Develop Write use case diagrams use case and scenario descriptions Develop activity diagrams and system sequence diagrams Refine and enhance the domain model class diagram Explain how UML diagrams work together to define functional requirements for the objectoriented approach Systems Analysis and Design in a Changing World, 3rd Edition 2 7 Overview Objective of requirements definition is understanding user’s needs, business processes, and system to support business processes Understand and define requirements for a new system using object-oriented analysis models and techniques Line between object-oriented analysis and objectoriented design is somewhat fuzzy Iterative approach to development Models built in analysis are refined during design Systems Analysis and Design in a Changing World, 3rd Edition 3 The Unified Modeling Language and the Object Management Group 7 Object-oriented modeling notation is Unified Modeling Language (UML) UML was presented to Object Management Group (OMG) as standard modeling technique Purpose of Object Management Group Promote theory and practice of object technology for development of distributed systems Provide common architectural framework for OO Systems Analysis and Design in a Changing World, 3rd Edition 4 7 Object-Oriented Requirements Object-oriented system requirements are specified and documented through process of building models Systems development process starts with identification of events and things Events are business processes that new system must address Things are problem domain objects involved in business process Systems Analysis and Design in a Changing World, 3rd Edition 5 7 Object-Oriented Approach Models Class diagram – definition of system components case diagrams and use case descriptions – show user roles and how they use the system Use sequence diagrams (SSDs) – define inputs and outputs and sequence of interactions between user and system for a use case Systems Statechart diagrams – describe states of each object Activity diagrams – describe user activities Systems Analysis and Design in a Changing World, 3rd Edition 6 Requirements Diagrams: Traditional and OO Models Systems Analysis and Design in a Changing World, 3rd Edition 7 7 The System Activities – A Use Case / Scenario View 7 Use case analysis used to identify and define all business processes that system must support Use Case - single function performed by system for those who use that function Actors Role played by user Outside automation boundary and organization Systems Analysis and Design in a Changing World, 3rd Edition 8 7 Use Case Diagram Graphical models that summarize information about actors and use cases System developer Looks at system as whole Identifies major uses from event table Identifies functions to be supported by new system Organizes use cases Systems Analysis and Design in a Changing World, 3rd Edition 9 7 Simple Use Case with an Actor Systems Analysis and Design in a Changing World, 3rd Edition 10 7 Use Case Diagram with System Boundary Systems Analysis and Design in a Changing World, 3rd Edition 11 7 Use Case of Customer Support System Systems Analysis and Design in a Changing World, 3rd Edition 12 7 All Use Cases Including Customer Systems Analysis and Design in a Changing World, 3rd Edition 13 7 Relationships Documents situation where one use case requires the services of a common subroutine Another use case is developed for this common subroutine A common use case can be reused by multiple use cases Systems Analysis and Design in a Changing World, 3rd Edition 14 Example of Order-Entry Subsystem with Use Cases Systems Analysis and Design in a Changing World, 3rd Edition 7 15 7 Developing a Use Case Diagram Starting points for use case development Use event table Identify all actors of the system Identify functions actors perform with system Develop flow of activities to identify various scenarios Common internal use cases can be identified and separated into different use cases Systems Analysis and Design in a Changing World, 3rd Edition 16 7 CRUD analysis CRUD – Create, Read/Report, Update, Delete Information Engineering (IE) technique to identify event table events or develop use case diagram Compares identified use cases with domain model class diagram Every class in class diagram must have use cases to support creating, reading, reporting, updating, and deleting object instances Confirms system integration requirements Systems Analysis and Design in a Changing World, 3rd Edition 17 7 Use Case Detailed Descriptions Scenario, or use case instance, details sequence of activities within use case Shows actor interacting with computer system step-by-step to carry out business activity May have several scenarios for single use case Analysts prefer to write narrative descriptions of use cases instead of building activity diagrams Three levels: brief, intermediate, and fully developed description Systems Analysis and Design in a Changing World, 3rd Edition 18 Brief Description of Create New Order Use Case Systems Analysis and Design in a Changing World, 3rd Edition 7 19 Intermediate Description of the Telephone Order Scenario for Create New Order Systems Analysis and Design in a Changing World, 3rd Edition 7 20 Intermediate Description of the Web Order Scenario for Create New Order Systems Analysis and Design in a Changing World, 3rd Edition 7 21 Fully Developed Description of Telephone Order Scenario for Create New Order Systems Analysis and Design in a Changing World, 3rd Edition 7 22 Fully Developed Description of Web Order Scenario for Create New Order Systems Analysis and Design in a Changing World, 3rd Edition 7 23 7 Activity Diagrams Used to document work flow of business process activities for each use case scenario Standard Can UML diagram support any level of use case description Helpful in developing system sequence diagrams Systems Analysis and Design in a Changing World, 3rd Edition 24 7 Activity Diagram: Telephone Order Scenario Systems Analysis and Design in a Changing World, 3rd Edition 25 7 Activity Diagram: Web Order Scenario Systems Analysis and Design in a Changing World, 3rd Edition 26 Identifying Inputs and Outputs – The System Sequence Diagram Collaboration diagram Emphasizes objects that interact together to support a use case diagram May be used alone or with sequence diagram System 7 sequence diagram Shows sequence of interactions between objects and flow of events in a single use case Focuses on message details Used more frequently in industry Systems Analysis and Design in a Changing World, 3rd Edition 27 7 Sample System Sequence Diagram (SSD) Systems Analysis and Design in a Changing World, 3rd Edition 28 7 SSD Notation represented by stick figure – person (or role) that “interacts” with system by entering input data and receiving output data Actor Object notation is rectangle with name of object underlined – shows individual object and not class of all similar objects Lifeline is vertical line under object or actor to show passage of time for object Messages use arrows to show messages sent or received by actor or system Systems Analysis and Design in a Changing World, 3rd Edition 29 7 SSD Lifelines Vertical If line under object or actor: Shows passage of time vertical line dashed: Creation and destruction of thing is not important for scenario Long narrow rectangles: Activation lifelines emphasize that object is active only during part of scenario Systems Analysis and Design in a Changing World, 3rd Edition 30 7 SSD Messages Internal events identified by the flow of objects within a scenario Requests from one actor or object to another to do some action Invokes a particular method Systems Analysis and Design in a Changing World, 3rd Edition 31 7 Repeating Message Systems Analysis and Design in a Changing World, 3rd Edition 32 7 Developing a System Sequence Diagram Begin with detailed description of use case from fully developed form or activity diagrams Identify input messages Describe message from external actor to system using message notation Identify and add any special conditions on input message, including iteration and true/false conditions Identify and add output return messages Systems Analysis and Design in a Changing World, 3rd Edition 33 Simplified Activity Diagram of the Telephone Order Scenario Systems Analysis and Design in a Changing World, 3rd Edition 7 34 7 SSD of Simplified Telephone Order Scenario for Create New Order Use Case Systems Analysis and Design in a Changing World, 3rd Edition 35 SSD of the Web Order Scenario for the Create New Order Use Case Systems Analysis and Design in a Changing World, 3rd Edition 7 36 Problem Domain Modeling – The Domain Model Class Diagram 7 Class diagram is focal point of object-oriented development Provides definition of system components Contains important class structural information for implementation with object-oriented programming Provides conceptual data model to describe classes for database definition Consists of problem domain classes and implementation classes Systems Analysis and Design in a Changing World, 3rd Edition 37 7 Example of Domain Model Class Diagram Systems Analysis and Design in a Changing World, 3rd Edition 38 7 RMO Domain Model Class Diagram Systems Analysis and Design in a Changing World, 3rd Edition 39 7 Integrating Object-Oriented Models Complete use case diagram is needed to understand total scope of new system Domain model class diagrams also should be as complete as possible for entire system With iterative approach, only construct use case descriptions, activity diagrams, and system sequence diagrams for use cases in iteration Development of a new diagram often helps refine and correct previous diagrams Systems Analysis and Design in a Changing World, 3rd Edition 40 Relationships Between OO Requirements Models Systems Analysis and Design in a Changing World, 3rd Edition 7 41 7 Use Case Diagram for Inventory System Systems Analysis and Design in a Changing World, 3rd Edition 42 7 Summary Object-oriented approach has complete set of diagrams that together document the user’s need and define system requirements Requirements specified using following models: Domain model class diagrams Use case diagrams Use case detailed model, either descriptive format or activity diagram System sequence diagrams (SSDs) Systems Analysis and Design in a Changing World, 3rd Edition 43 What makes a system sequence diagram SSD different from an activity diagram?Differences Between Sequence Diagram and Activity Diagram
The Sequence diagram shows the message flow from one object to another object. The Activity diagram shows the message flow from one activity to another.
What is the use of activity diagram to the system developer?Using activity diagrams in system development
They help to visualize the functionality of the system at different levels of detail, and aid communication between developers and clients.
What is the most important aspect of a sequence diagram?Messages are the most important elements of a sequence diagram. They indicate when one object calls an operation on another object (or itself). They are also used to indicate return values.
What is the purpose of active diagram?Activity diagrams are similar to flowcharts because they show the flow between the actions in an activity; however, activity diagrams can also show parallel or concurrent flows and alternate flows. In activity diagrams, you use activity nodes and activity edges to model the flow of control and data between actions.
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Activity diagrams are not helpful in developing system sequence diagrams (ssds).
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