1 / 26

Information System

Information System. IS: a set of related components working together in some environment to perform functions that achieve some objective. Organizational policies. Process. Input. Output. Standard operating procedures. Customers. Government Regulations. Shippers. Competitors.

daria-castaneda
Download Presentation

Information System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Information System • IS: a set of related components working together in some environment to perform functions that achieve some objective.

  2. Organizational policies Process Input Output Standard operating procedures Customers Government Regulations Shippers Competitors

  3. IS Functions • Input, Processing, Output, Storage, Controls • IS Components • People, Procedures, Data, Software, Hardware Alternative: Object-oriented view of a system

  4. Object-Oriented Systems • Object • Attributes - characterize an object • Methods - the object’s behavior DOG DOG OWNER VET Name Sex Breed Name Address Name Speciality Throw MakePayment GiveTreatment BillCustomer fetch

  5. Object class • set of objects with common attributes and functions • Object Instance • has specific values for attributes • can perform all methods of the class

  6. O-O systems: Inheritance People Vet Dog Owner . . Cathy Fred People Vet DogOwner Fred Cathy

  7. O-O systems: Inheritance People Dog Owner Vet . . Fred Cathy People Vet DogOwner Multiple inheritance Cathy Fred

  8. Systems Development: the process • System lifecycle: • development phase * • production phase • Systems approach • divide and conquer conversion

  9. Systems Development: the process • System Analysis • study business problem domain, existing system • identify requirements • specify characteristics of new system • System decomposition • by functions performed • in terms of objects

  10. Systems Development: the process • System Design • evaluate alternative solutions, design a chosen solution • design document: basis for implementation

  11. Two system development approaches • Functional Decomposition • identify major activities, break up into composite steps (structured analysis and design) • focus on verbs (what a system does) • Objects that comprise the system and how they act and relate • object structure and behavior analysis • focus on nouns (objects performing functions)

  12. SDLC • System development methodology • activities to solve a problem • A methodology uses certain techniques (used to model a system) • Model • representation of real world • used in analyzing and communicating what we understand DATA MODELS, PROCESS MODELS, OBJECT MODELS, etc.

  13. System development catalysts • User demand problems in current system, need for enhancements, improved efficiency • Technology push new technology as catalysts • Strategic pull system to support new business strategies/ products to stay competitive

  14. Projects of varying complexity • Upto 1000 lines • trivial, single person, few days/week • 1000-10,000 lines • simple, 3/4 progr/analyst, 6-12 months • often formal analysis and design not used, but could be - leads to more maintainable system • 10,000-100,000 lines • difficult, 6-12 people, 2-3 years • formal analysis and design essential • requirements/users change over time • 100,000 - 1 million lines • complex. 50-100 people, 3-5 years • diverse community of users • 1-10 million lines • nearly impossible • > 10 million • absurd??

  15. Why do IS projects fail? • Did not support business strategy & objectives • poor planning, project management • failure to understand user requirements • user involvement in system development • inadequate cost vs. benefit analysis • escalating costs, intangible benefits • myriad of design defects/ errors • installation of incompatible or inadequate technology • no adequate controls implemented • unstructured, un-maintainable software

  16. Successful systems development • Informal, sloppy art structured, engineered and managed approach (SDLC) • stress user involvement in system development • system planning and project management • evaluate alternate designs before committing • clean, complete and up-to-date documentation • design for growth and change

  17. Bugs! • software errors cost U.S. users $59.5 billion each year.(National Institute of Standards and Technology (NIST) • just the cost of routine work-arounds and corrections by users, along with the added cost of buggy software that had to be fixed late in the development process. The real cost of bugs is much higher. • $22.2 billion of that $59.5 billion, or 37%, could be saved through "feasible improvements" in software testing. • “We indulge ourselves with the idea that all software has bugs, so trying harder to get rid of them is pointless perfectionism. Intellectually we should know better” !

  18. Software: the product • Software: a strategic business issue, not just a low-level support activity • Can software be “manufactured” like physical products? (software “factories”) • Costs are concentrated on engineering (design) and support • “mythical man-month” Adding people to a project that is late will only worsen the situation. Why? • Efficiency through re-use

  19. Failure Curves Wear out Changes Infant mortality Failure Rate Actual Ideal Time Hardware Software

  20. The Systems Analyst • Roles • as a CONSULTANT (external) • provide a fresh perspective • disadvantage: organizational culture may not be known • as a SUPPORTING EXPERT • as a CATALYST FOR CHANGE • interact with management • excellent with people and machines • analyze need for change, design change with consensus, implement change

  21. The Systems Analyst • Qualities • problem solver • good analysis skills • tools and techniques for analysis • communicator • computer skills • knowledge of business processes • self-disciplined and self-motivated

  22. IS Building Blocks • People • Data • Activities • Networks • Technology

  23. IS Building Blocks: PEOPLE • System Owners • sponsors, advocates • budgeting, time and money • responsible for ultimate acceptance • System users • need for communication with users during A&D • different user groups with diff. info. Needs • System designers • translate business/user requirements and constraints into technical solutions • System builders • implement system based on design specifications

  24. IS building blocks: DATA • System owners’ view • info. on business resources • avoid details, focus on business entities of interest • System users’ view • data experts, how data is used • identify data requirements, independent of implementation (entities, attributes, and rules) • System designers’ view • files and databases • System builders’ view • implement files, DBs, etc.

  25. IS building blocks: ACTIVITIES • System owners view • “big picture” • System users view • distinct processes and their detail • SA elicits processing requirements from users [NOTE:users often biased by current system] • System designers view • technology constraints • specifications [DFDs, structure charts, E/R, etc] • System builders view • application programs

  26. IS building blocks: NETWORKS (distributed people, processes, data) • System owners view • geographic scope, locations • System users view • details, data flow between locations, local data storage • System designers view • system architecture, sharing/duplication of data, communication between machines • System builders view • network control programs

More Related