Object-Oriented Analysis and Design

Object-Oriented Analysis and Design. Lecture 6: DESign activities and use case realization. Objectives. Design Discipline Design Activities Develop detailed object-oriented design models Design class diagrams Extend domain model. Moving From Business Modeling Requirements to Design.
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Object-Oriented Analysis and DesignLecture 6: DESign activities and use case realizationObjectives
  • Design Discipline
  • Design Activities
  • Develop detailed object-oriented design models
  • Design class diagrams
  • Extend domain model
  • Moving From Business Modeling Requirements to Design
  • Business and requirements models
  • Description: high-level representations
  • Needs, key processes and functions, environment
  • Purpose: promote understanding
  • Design models move project closer to implementation
  • Models of design discipline are “blueprints”
  • Design activities carry out business tasks and achieve business objectives  
  • Comparison of Modeling During the Business Modeling, Requirements, and Design DisciplinesDesign Activities in the UP Life CycleDesign Use Case Realizations
  • Use case realizations offer a lower-level view
  • Two-tiered focus
  • Class interactions supporting a particular use case
  • Interactions among software, users, and external systems
  • Design typically spread over many iterations
  • UML design class diagrams and interaction diagrams document design
  • Design the Database
  • Designing database as a key design activity
  • Physical model of database based on class diagram
  • Physical model describes relational or OO database
  • Some technical issues
  • Performance, such as response time
  • Integration with existing databases
  • Legacy databases
  • Design the User Interface
  • User interface issues
  • User capabilities and needs differ widely
  • User interacts with the system in different ways
  • Approaches to interface vary by system
  • Has nature of interface emerged from earlier models?
  • What is Object-Oriented Design?
  • The bridge between a user’s requirements and programming for the new system
  • “Blueprints”, or design models, are necessary to build systems
  • An adaptive approach to development
  • Requirements and design are done incrementally within an iteration
  • A complete set of designs may not be developed at one time
  • Overview of Object-Oriented Programs
  • Object-oriented programs consist of a set of computing objects that cooperate to accomplish a result
  • Each object has program logic and data encapsulated within it
  • Objects send each other messages to collaborate
  • Most object-oriented programs are event-driven
  • Instantiation of a class creates an object based on the template provided by the class definition
  • Object-oriented event-driven program flowObject-Oriented Design Models
  • Identify all objects that must work together to carry out a use case
  • Divide objects into groups for a multilayer design
  • Interaction diagrams describe the messages that are sent between objects
  • Includes sequence and communication diagrams
  • Design class diagrams document and describe the programming classes
  • Design class for Student classDesign models with their respective input modelsObject-Oriented Design Process
  • Create a first-cut model of the design class diagrams
  • Develop interaction diagrams for each use case or scenario
  • Update the design class diagrams
  • Method names, attributes, and navigation visibility
  • Design Classes and Design Class Diagrams
  • Design class diagrams are extensions of domain class model diagrams
  • Elaborate on attribute details
  • Define parameters and return values of methods
  • Define the internal logic of methods
  • A first-cut design class diagram is based on the domain model and engineering design principles
  • Interaction diagrams are used to refine a design class diagram as development progresses
  • Design Class Notation
  • Class name and stereotype information
  • Attribute information
  • Visibility, type-expression, name, initial value, and properties
  • Method signature
  • Visibility, name, type-expression, and parameter list
  • Use the entire signature to identify a method to distinguish between overloaded methods
  • OStudentclass examples for the domain diagram and the design class diagramDeveloping the First-Cut Design Class Diagram
  • Elaborate the attributes with type and initial value information
  • Most attributes should be private
  • Add navigation visibility arrows
  • Based on which classes need access to which other classes
  • Can be bidirectional
  • Will need to be updated as design progresses
  • First-cut RMO design class diagramInteraction Diagrams–Realizing Use Cases and Defining Methods
  • Interaction diagrams are at the heart of object-oriented design
  • Realization of a use case
  • Determine what objects collaborate by sending messages to each other
  • Two types
  • Sequence
  • Communication
  • Object Responsibility
  • Objects are responsible for carrying out system processing
  • Two major areas of responsibility
  • Knowing
  • Knowledge about its own data and about other classes with which it must collaborate to carry out use cases
  • Doing
  • All the activities an object does to assist in the execution of a use case
  • Partial design class diagram for the Look up item availability use caseDesigning with Sequence Diagrams
  • An SSD captures the interactions between the system and the external world represented by actors
  • The system is treated like a black box
  • A detailed sequence diagram uses all of the same elements as an SSD
  • The :System object is replaced by all of the internal objects and messages within the system
  • SSD for the Look up item availability use caseFirst-Cut Sequence Diagram
  • Determine which other objects may need to be involved to carry out the use case
  • Replace the :System object with a use case controller object
  • Determine which other messages will be sent
  • Define the source and destination object for each message
  • Use activation lifelines to indicate when an object is executing a method
  • First-cut sequence diagram for the Look up item availability use caseGuidelines for Preliminary Sequence Diagram Development
  • Determine all of the internal messages that result from each input message
  • Define origin and destination objects
  • Identify the complete set of classes that will be affected by each message
  • Flesh out the components for each message
  • Iteration, true/false conditions, return values, and passed parameters
  • SSD for the telephone order scenario of the Create new order use caseSequence diagram for thetelephone order scenario of the Create new order use case
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