Finalizing Design Specifications Modern Systems Analysis and Design Finalizing Design Specifications

Learning Objectives Discuss how the need for system design specifications varies by system development methodology. Define quality requirements and write quality requirement statements. Chapter 13 © 2008 by Prentice Hall

Learning Objectives Read and understand a structure chart. Explain the roles of prototyping and CASE tools in capturing design specifications. Chapter 13 © 2008 by Prentice Hall

Learning Objectives (Cont.) Discuss how design specifications apply (or do not apply) to Agile Methodologies. Demonstrate how to declare design specifications for electronic commerce applications. Chapter 13 © 2008 by Prentice Hall

Finalizing Design Specifications Chapter 13 © 2008 by Prentice Hall

The Process of Finalizing Design Specifications Less costly to correct and detect errors during the design phase. Take logical design information and turn it into a blueprint for the physical information system. Chapter 13 © 2008 by Prentice Hall

The Process of Finalizing Design Specifications Can be paper-based or computer-based. Can be written, graphical, or combination of the two. Chapter 13 © 2008 by Prentice Hall

The Process of Finalizing Design Specifications (Cont.) Can be high-level broad-based or detailed as possible. Format and amount of detail will be driven by intended audience. Chapter 13 © 2008 by Prentice Hall

The Process of Finalizing Design Specifications (Cont.) Good specifications should be stated simply, completely, unambiguous, and have attributes that make requirements more understandable. Chapter 13 © 2008 by Prentice Hall

Deliverables and Outcomes for Traditional Projects A set of physical design specifications for the entire system, including detailed specifications for each separate part of the system. Include functional descriptions for each part of the system. input received and output generated for each program and its component parts. Chapter 13 © 2008 by Prentice Hall

Deliverables and Outcomes for Traditional Projects (Cont.) Complete design specification is comprehensive. Design specifications can be based on: Traditional methods. Agile methodologies (eXtreme programming). Chapter 13 © 2008 by Prentice Hall

Specification Documents Contains: Overall system description. Interface requirements. System features. Nonfunctional requirements. Other requirements. Supporting diagrams and models. Chapter 13 © 2008 by Prentice Hall

Specification Documents (Cont.) Computer-based requirements management tools make it easier to keep documents up to date, add additional requirements and link related requirements. Chapter 13 © 2008 by Prentice Hall

Specification Documents (Cont.) Figure 13-3 A screen from DOORS© Enterprise Requirements Suite (a product of Telelogic AB) Chapter 13 © 2008 by Prentice Hall

Specification Documents (Cont.) Figure 13-4 A screen from Compuware Optimal Trace requirements management and definition solution Chapter 13 © 2008 by Prentice Hall

Structure Chart Structure Chart: a hierarchical diagram that shows how an information system is organized. Shows how an information system is organized in hierarchical models. Shows how parts of a system are related to one another. Shows breakdown of a system into programs and internal structures of programs written in third- and fourth-generation languages. Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Structure chart is composed of modules. Modules: a self-contained component of a system that is defined by its function. Functions or subroutines in the resulting computer program (COBOL, BASIC, FORTRAN). Method in object-oriented language. Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Figure 13-5 An illustration of the hierarchy of a structure chart Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Data couple: a diagrammatic representation of the data exchanges between two modules in a structure chart. Flag: a diagrammatic representation of a message passed between two modules. Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Figure 13-6 Special symbols used in structure charts – Data couples and control flag Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Figure 13-7 How to read a structure chart – (a) Nonoverlapping arrows Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Figure 13-7 How to read a structure chart – (b) Overlapping arrows Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Pseudocode: a method for representing the instructions in a module with language very similar to computer programming code. Chapter 13 © 2008 by Prentice Hall

Structure Chart (Cont.) Serves two functions: Helps analyst think in a structured way about the task a module is designed to perform. Acts as a communication tool between analyst and programmer. Chapter 13 © 2008 by Prentice Hall

Evolutionary Prototyping Begin by modeling parts of the target system. If successful, evolve remaining system from prototype. Prototype becomes actual production system. Chapter 13 © 2008 by Prentice Hall

Evolutionary Prototyping (Cont.) Often, difficult parts of the system are prototyped first. Exception handling must be added to prototype. Chapter 13 © 2008 by Prentice Hall

Evolutionary Prototyping (Cont.) Figure 13-8 McConnell’s evolutionary prototyping model Chapter 13 © 2008 by Prentice Hall

Throwaway Prototyping Prototype is not preserved. It is developed quickly to demonstrate unclear aspect of system design. CASE tools aid this approach. Chapter 13 © 2008 by Prentice Hall

Throwaway Prototyping (Cont.) Figure 13-9 A prototype of Hoosier Burger’s inventory control system generated with Oracle’s Designer CASE tools. Chapter 13 © 2008 by Prentice Hall

Rapid Application Development Rapid Application Development (RAD) has four life cycle phases: Planning Design Construction Cutover Chapter 13 © 2008 by Prentice Hall

Rapid Application Development (Cont.) RAD Trends: Heavy iteration between the design phase where requirements are captured; And heavy iteration in the construction phase where the system is designed and built. Chapter 13 © 2008 by Prentice Hall

Agile Methodologies Traditional approach: Agile approach: Analysis  design  code  test loop Agile approach: Design specifications come from code instead of verbal text descriptions. Requirements  design  code Best known method: eXtreme programming or XP. Chapter 13 © 2008 by Prentice Hall

Agile Methodologies (Cont.) Figure 13-11 The analyze-design-code-test cycle Chapter 13 © 2008 by Prentice Hall

Agile Methodologies (Cont.) Simple design: the creation of uncomplicated software and software components that work to solve current the current problem rather than the creation of complicated software designed for a future that may not come. Chapter 13 © 2008 by Prentice Hall

Agile Methodologies (Cont.) Simple design reflects one of the key values of eXtreme Programming – simplicity. Refactoring: making a program simpler after adding a new feature. Chapter 13 © 2008 by Prentice Hall

Agile Methodologies (Cont.) XP has four constraints that facilitate simple design: The system must communicate everything you want it to communicate. The system must contain no duplicate code. Chapter 13 © 2008 by Prentice Hall

Agile Methodologies (Cont.) The system should have the fewest possible classes. The system should have the fewest possible methods. Chapter 13 © 2008 by Prentice Hall

Finalizing design specifications. Electronic Commerce Application: Finalizing Design Specifications for Pine Valley Furniture’s WebStore Finalizing design specifications. Defined required fields for each of the pages identified in the design phase. Chapter 13 © 2008 by Prentice Hall

The four key features of the human-computer interface PVF wanted: Electronic Commerce Application: Finalizing Design Specifications for Pine Valley Furniture’s WebStore The four key features of the human-computer interface PVF wanted: Menu-driven navigation with cookie crumbs. Lightweight graphics. Form and data integrity rules. Template-based HTML. Chapter 13 © 2008 by Prentice Hall

Electronic Commerce Application: Finalizing Design Specifications for Pine Valley Furniture’s WebStore Figure 13-13 – (a) The Home page within the WebStore throwaway prototype Chapter 13 © 2008 by Prentice Hall

Summary In this chapter you learned how to: Discuss how the need for system design specifications varies by system development methodology. Define quality requirements and write quality requirement statements. Chapter 13 © 2008 by Prentice Hall

Summary (Cont.) Read and understand a structure chart. Explain the roles of prototyping and CASE tools in capturing design specifications. Chapter 13 © 2008 by Prentice Hall

Summary (Cont.) Discuss how design specifications apply (or do not apply) to Agile Methodologies. Demonstrate how to declare design specifications for electronic commerce applications. Chapter 13 © 2008 by Prentice Hall