Presentation on theme: "Logical and Physical Design of an Information System"— Presentation transcript:
1 Logical and Physical Design of an Information System
2 Logical Design of an ISYou develop the logical design of an information system during the systems analysis phase.The logical design defines the functions and features of the system and the relationship among its components.The logical design includes the output that must be produced by the system, the input needed by the system, and the process that must be produced by the system without regard to how tasks will be accomplished physically.
3 Logical Design of an ISa logical design defines what must take place, not how it is to be accomplished.logical designs do not address the actual methods of implementation.
4 Example:The Logical Design of a Customer Record Systemdescribes the data that must be entered for each customerspecifies that records must be displayed in customer number order, andexplains what information to produce for a customer status reportSpecifications for the actual input, or entry, of data, the sorting method, the physical process of creating the report, and the exact format of the report are not part of the logical design.
5 Physical Design of an IS the physical design of an information system is a plan for the actual implementation of the system.you develop the physical design during the systems design phase.the physical design is built on the system’s logical design and describes a specific implementation, much like a working blue print describes the actual construction of a building.
6 Physical Design of an IS the physical design describes the actual processes of entering, verifying, and storing data; the physical layout of data files; the sorting procedures; the exact format of reports; and so on.Whereas logical design is concerned with what the system must accomplish, physical design is concerned with how the system will meet those requirements.
7 The relationship of Logical and Physical design good system design is impossible without careful, accurate system analysis.the design phase typically cannot begin until the analysis work is complete. It is better to complete the analysis phase before moving on to systems design.
9 Three (3) main activities of system analysis phase: STEPACTIVITYDESCRIPTION1Requirements modelingInvolves fact-finding to describe the current system and identification of the requirement s for the new system, such as outputs, inputs, processes, performance, and security.2Data and process modelingA graphically modeling process to represent system data and process using traditional structured analysis techniques. Structured analysis identifies the data flowing into a process, the business rules that transform the data, and the resulting output data flow.
10 Development strategies STEPACTIVITYDESCRIPTION3Development strategiesIn development strategies, you will consider various options and prepare for the transition to the systems design phase.The deliverable, or end product, of the system analysis phase is a system requirement document, which is an overall design for the new system
12 Three (3) main activities of system design phase: STEPACTIVITYDESCRIPTION1Review system requirementsBecome familiar with the logical design.2Design the systemUser interfaceDesign an overall user interface, including screens, commands, controls, and features that enable users to interact with the application.Input processesDetermine how data will be input to the system and design necessary source documents.
13 STEPACTIVITYDESCRIPTIONInput and outputDesign the physical layout for each input and output formats and reports screen and printed reports.DataDetermine how data will be organized, stored, maintained, updated, accessed, and used.System ArchitectureDetermine processing strategies and methods, client/server interaction, network configuration, and internet/intranet interface issues.
14 Present the system design STEPACTIVITYDESCRIPTION3Present the system designCreate the system design specification document, in which you describe the proposed system design, the anticipated benefits of the system, and the estimated development and implementation costs.
15 SYSTEM DESIGN CONSIDERATIONS User Consideration Data ConsiderationArchitecture ConsiderationConsider points where users interact with the systemAnticipate future user, system, and organizational needsEnter data where and when it occursVerify data where it is inputUse automated data entry methods whenever possibleControl access for data entryReport every instances of entry and change of dataEnter data only onceUse a modular designDesign independent modules that perform a single function
16 Logical System Design (System Analysis Phase) Data Flow DiagramsData DictionaryProcess DescriptionsPhysical System Design (System Design Phase)Entity-Relationship DiagramNormalization of DatabaseUser Interface and Reports