9 Systems Analysis and Design in a Changing World, Fourth Edition

9 Systems Analysis and Design in a Changing World, 4th Edition 2 Learning Objectives u Discuss the issues related to managing and coordinating the design phase of the SDLC u Explain the major components and levels of design u Describe each design phase activity u Describe common deployment environments and matching application architectures u Develop a simple network diagram and estimate communication capacity requirements

9 Systems Analysis and Design in a Changing World, 4th Edition 3 Overview u This chapter l Completes the transition from analysis to design l Discusses issues related to design of new system l Describes all design phase activities l Describes network and architecture design u Analysis focuses on what system should do— business requirements u Design is oriented toward how system will be built —defining structural components

9 Systems Analysis and Design in a Changing World, 4th Edition 4 Understanding the Elements of Design u Design is process of describing, organizing, and structuring system components at architectural design level and detailed design level l Focused on preparing for construction l Like developing blueprints u Three questions l What components require systems design? l What are inputs to and outputs of design process? l How is systems design done?

9 Systems Analysis and Design in a Changing World, 4th Edition 5 Components Requiring Systems Design

9 Systems Analysis and Design in a Changing World, 4th Edition 6 Analysis Objectives to Design Objectives

9 Systems Analysis and Design in a Changing World, 4th Edition 7 Moving from Analysis to Design u Design l Converts functional models from analysis into models that represent the solution l Focused on technical issues l Requires less user involvement than analysis u Design may use structured or OO approaches l Database can be relational, OO, or hybrid l User interface issues

9 Systems Analysis and Design in a Changing World, 4th Edition 8 Traditional Structured and Object- Oriented Models (Figure 9-3)

9 Systems Analysis and Design in a Changing World, 4th Edition 9 SDLC Phases with Design Phase Activities

9 Systems Analysis and Design in a Changing World, 4th Edition 10 Design Phase Activities and Key Questions (Figure 9-5)

9 Systems Analysis and Design in a Changing World, 4th Edition 11 Design and Integrate the Network u Network specialists establish network based on strategic plan u Project team typically integrates system into existing network u Technical requirements have to do with communication via networks u Technical issues handled by network specialists l Reliability, security, throughput, synchronization

9 Systems Analysis and Design in a Changing World, 4th Edition 12 Design the Application Architecture u Specify how system use cases are carried out u Described during system analysis as logical models of system activities u After design alternative is selected, detailed computer processing is designed as physical models, such as physical data flow diagrams and structure charts (traditional) or interaction diagrams and class diagrams (OO) u Approach varies depending on development and deployment environments

9 Systems Analysis and Design in a Changing World, 4th Edition 13 Design the User Interfaces u User interface quality is critical aspect of system u Design of user interface defines how user interacts with system l GUI – windows, dialog boxes, mouse interaction l Sound, video, voice commands u To user of system, user interface is the system u User interface specialists – interface designers, usability consultants, human factors engineers

9 Systems Analysis and Design in a Changing World, 4th Edition 14 Design the System Interfaces u System interfaces enable systems to share and exchange information l Internal organization systems l Interfaces with systems outside organization l New system interfaces with package application that organization has purchased and installed u System interfaces can be complex u Organization needs very specialized technical skills to work on these interfaces

9 Systems Analysis and Design in a Changing World, 4th Edition 15 Design and Integrate the Database u System analysis data model used to create physical database model u Collection of traditional computer files, relational databases, and/or object-oriented databases u Technical requirements, such as response times, determine database performance needs u Design work might involve l Performance tuning l Integration between new and existing databases

9 Systems Analysis and Design in a Changing World, 4th Edition 16 Prototype for Design Details u Continue to create and evaluate prototypes during design phase u Prototypes confirm design choices l Database l Network architecture l Controls l Programming environment u Rapid application development (RAD) design prototypes evolve into finished system

9 Systems Analysis and Design in a Changing World, 4th Edition 17 Design and Integrate the System Controls u Final design activity to ensure system has adequate safeguards (system controls) to protect organizational assets u Controls are needed for all other design activities l User interface – limit access to authorized users l System interface – protect from other systems l Application architecture – record transactions l Database – protect from software/hardware failure l Network design – protect communications

9 Systems Analysis and Design in a Changing World, 4th Edition 18 Project Management—Coordinating the Project u Manage changing requirements u Coordinate design elements u Coordinate project teams l Project schedule - coordinate ongoing work u Coordinate information l CASE tools and central repository l Team communication and information coordination l Track open items and unresolved issues

9 Systems Analysis and Design in a Changing World, 4th Edition 19 System Development Information Stored in the CASE Repository (Figure 9-6)

9 Systems Analysis and Design in a Changing World, 4th Edition 20 Deployment Environment u Deployment environment definition bridges analysis and design l Hardware l System software l Networking u Common deployment environments in which system will operate u Related design patterns and architectures for application software

9 Systems Analysis and Design in a Changing World, 4th Edition 21 Single-Computer and Multitier Architecture u Single-computer architecture l Mainframe-based l Limited by single machine capacity u Clustered and multi-computer architecture l Group of computers to provide processing and data storage capacity l Cluster acts as a single system l Multicomputer hardware/OS can be less similar than clustered

9 Systems Analysis and Design in a Changing World, 4th Edition 22 Single-, Clustered, and Multicomputer Architectures

9 Systems Analysis and Design in a Changing World, 4th Edition 23 Centralized and Distributed Architecture u Distributes system across several computers and locations u Relies on communication networks for geographic connectivity u Client/server architecture dominant model for distributed computing

9 Systems Analysis and Design in a Changing World, 4th Edition 24 Computer Network u Set of transmission lines, specialized hardware, and communication protocols u Enables communication among different users and computer systems u Local area network (LAN) less than one kilometer long – connects computers within single building u Wide area network (WAN) over one kilometer long – implies much greater, global, distances u Router – directs information within network

9 Systems Analysis and Design in a Changing World, 4th Edition 25 A Possible Network Configuration for RMO

9 Systems Analysis and Design in a Changing World, 4th Edition 26 The Internet, Intranets, and Extranets u Internet – global collection of networks that use TCP/IP networking protocols u Intranets l Private networks using same TCP/IP protocols as the Internet l Limited to internal users u Extranets l Intranets that have been extended outside the organization

9 Systems Analysis and Design in a Changing World, 4th Edition 27 Application Architecture u Complex hardware/networks require more complex software architectures u There are commonly used approaches (patterns) for application architecture l Client/server architecture l Three-layer client/server architecture l Web services architecture l Internet and Web-based application architecture

9 Systems Analysis and Design in a Changing World, 4th Edition 28 Client/Server Architecture u Client/server divides programs into two types u Server – manages information system resources or provides well-defined services for client u Client – communicates with server to request resources or services u Advantage – deployment flexibility l Location, scalability, maintainability u Disadvantage – complexity l Performance, security, and reliability

9 Systems Analysis and Design in a Changing World, 4th Edition 29 Interaction Among Multiple Clients and a Single Server (Figure 9-11)

9 Systems Analysis and Design in a Changing World, 4th Edition 30 Client/Server Architectural Process u Decompose application into client and server programs, modules, or objects l Identify resources or services that can be centrally managed by independent software units u Determine which clients and servers will execute on which computer systems u Describe communication protocols and networks that connect clients and servers

9 Systems Analysis and Design in a Changing World, 4th Edition 31 Three-Layer Client/Server Architecture u Layers can reside on one processor or be distributed to multiple processors u Data layer – manages access to stored data in databases u Business logic layer – implements rules and procedures of business processing u View layer – accepts user input and formats and displays processing results

9 Systems Analysis and Design in a Changing World, 4th Edition 32 Three-Layer Architecture

9 Systems Analysis and Design in a Changing World, 4th Edition 33 Web Services Architecture u A client/server architecture u Packages software functionality into server processes (“services”) u Makes services available to applications via Web protocols u Web services are available to internal and external applications l Developers can assemble an application using existing Web services

9 Systems Analysis and Design in a Changing World, 4th Edition 34 Web Services Architecture (Figure 9-13)

9 Systems Analysis and Design in a Changing World, 4th Edition 35 Middleware u Aspect of distributed computing u Connects parts of an application and enables requests and data to pass between them u Transaction process monitors, object request brokers (ORBs), Web services directories u Designers reply on standard frameworks and protocols incorporated into middleware

9 Systems Analysis and Design in a Changing World, 4th Edition 36 Internet and Web-Based Application Architecture u Web is complex example of client/server architecture u Can use Web protocols and browsers as application interfaces u Benefits l Accessibility l Low-cost communication l Widely implemented standards

9 Systems Analysis and Design in a Changing World, 4th Edition 37 Negative Aspects of Internet Application Delivery u Breaches of security u Fluctuating reliability of network throughput u Throughput can be limited u Volatile, changing standards

9 Systems Analysis and Design in a Changing World, 4th Edition 38 Network Design u Integrate network needs of new system into existing network infrastructure u Describe processing activity and network connectivity at each system location u Describe communications protocols and middleware that connects layers u Ensure that network capacity is sufficient l Data size per access type and average l Peak number of access per minute or hour

9 Systems Analysis and Design in a Changing World, 4th Edition 39 Network Diagram for RMO Customer Support System (Figure 9-14)

9 Systems Analysis and Design in a Changing World, 4th Edition 40 Summary u Systems design is process of organizing and structuring components of system to allow construction (programming) of new system u Design phase of project consists of activities that relate to design of components of new system l Application architecture, user interfaces, system interfaces, databases, network diagrams, system controls l Prototyping may be required to specify any part or all of the design

9 Systems Analysis and Design in a Changing World, 4th Edition 41 Summary ( continued ) u Inputs to design activities are diagrams built during analysis u Outputs of design are also diagrams that describe architecture of new system and detailed logic of programming components u Inputs, design activities, and outputs are different depending on whether a structured approach or an object-oriented approach is used u Architectural design adapts to development environment and decomposes design into layers