Information Systems Development (IS501) Dr.Doaa Nabil

1. Information Systems Development (IS501) Dr.Doaa Nabil

2. Chapter (1) System Development Life Cycle (SDLC)

3. Systems Development Life Cycle (SDLC) : is a general term used to describe the method and process of developing a new information system SDLC provides: Structure Methods Controls Checklist Result of that: successful developmentWithout that: risk for missed deadline, low quality .

4. SDLC Models A framework that describes the activities performed at each stage of a software development project.

5. SDLC Models (cont.) • Build-and-fix model • Waterfall model • Rapid prototyping model • Incremental model • Spiral model

6. Build-and-fix model • Building without specifications or attempt at design • Totally unsatisfactory for large projects • Difficult to maintain

8. Waterfall Model • Requirements – defines needed information, function, behavior, performance and interfaces( specification and planning). • Design – data structures, software architecture, interface representations, algorithmic details. • Implementation – source code, database, user documentation, testing, installation, and maintenance.

10. When to use the Waterfall Model • Requirements are very well known (A set of high quality, stable user requirements exist ) • Product definition is stable • Technology is understood • New version of an existing product • The user require all complete system at once • Previous experience of building similar systems exist • The duration of the project is two years or less

11. Waterfall Strengths • Easy to understand, easy to use • Provides structure to inexperienced staff • Milestones are well understood • Sets requirements stability • Good for management control (plan, staff, track) • Works well when quality is more important than cost or schedule

12. Waterfall Deficiencies • All requirements must be known upfront • Deliverables created for each phase are considered frozen – inhibits flexibility • Can give a false impression of progress • Does not reflect problem-solving nature of software development – iterations of phases • Integration is one big bang at the end • Little opportunity for customer to preview the system (until it may be too late)

13. Rapid Application Model (RAD) • Requirements planning phase (a workshop utilizing structured discussion of business problems) • User description phase – automated tools capture information from users • Construction phase – productivity tools, such as code generators, screen generators, etc. inside a time-box. (“Do until done”) • Cutover phase -- installation of the system, user acceptance testing and user training

15. When to use RAD • Reasonably well-known requirements • User involved throughout the life cycle • Project can be time-boxed • Functionality delivered in increments • High performance not required • Low technical risks • System can be modularized

16. RAD Strengths • Reduced cycle time and improved productivity with fewer people means lower costs • Time-box approach mitigates cost and schedule risk • Customer involved throughout the complete cycle minimizes risk of not achieving customer satisfaction and business needs • Focus moves from documentation to code . • Uses modeling concepts to capture information about business, data, and processes.

17. RAD Weaknesses • Accelerated development process must give quick responses to the user • Risk of never achieving closure • Hard to use with legacy systems • Requires a system that can be modularized • Developers and customers must be committed to rapid-fire activities in an abbreviated time frame.

18. Incremental SDLC Model • Construct a partial implementation of a total system • Then slowly add increased functionality • The incremental model prioritizes requirements of the system and then implements them in groups. • Each subsequent release of the system adds function to the previous release, until all designed functionality has been implemented.

20. When to use the Incremental Model • Risk, funding, schedule, program complexity, or need for early realization of benefits. • Most of the requirements are known up-front but are expected to evolve over time • A need to get basic functionality to the market early • On projects which have lengthy development schedules • On a project with new technology

21. Incremental Model Strengths • Develop high-risk or major functions first • Each release delivers an operational product • Customer can respond to each build • Uses “divide and conquer” breakdown of tasks • Lowers initial delivery cost • Initial product delivery is faster • Customers get important functionality early • Risk of changing requirements is reduced

22. Incremental Model Weaknesses • Requires good planning and design • Requires early definition of a complete and fully functional system to allow for the definition of increments • Well-defined module interfaces are required (some will be developed long before others) • Total cost of the complete system is not lower

23. Spiral SDLC Model • Adds risk analysis, and 4gl RAD prototyping to the waterfall model • Each cycle involves the same sequence of steps as the waterfall process model

24. When to use The spiral Model • Some user experience is required to refine and complete the requirements • Some parts of the implementation may depend on future technology • New user requirements are anticipated but not yet known • Some user requirements may be significantly more difficult to meet than others, and it is decided not to allow them to delay a usable delivery.

25. Spiral Quadrant • Determine objectives, alternatives and constraints • Evaluate alternatives, identify and resolve risks • Develop next-level product • Plan next phase

26. Spiral QuadrantDetermine objectives, alternatives and constraints • Objectives: functionality, performance,hardware/software interface, critical success factors, etc. • Alternatives: build, reuse, buy, sub-contract, etc. • Constraints: cost, schedule, interface, etc.

27. Spiral QuadrantEvaluate alternatives, identify and resolve risks • Study alternatives relative to objectives and constraints • Identify risks (lack of experience, new technology, tight schedules, poor process, etc. • Resolve risks (evaluate if money could be lost by continuing system development

28. Spiral QuadrantDevelop next-level product • Typical activities: • Create a design • Review design • Develop code • Inspect code • Test product

29. Spiral QuadrantPlan next phase • Typical activities • Develop project plan • Develop configuration management plan • Develop a test plan • Develop an installation plan

30. Spiral Model Strengths • Provides early indication of insurmountable risks, without much cost • Users see the system early because of rapid prototyping tools • Critical high-risk functions are developed first • The design does not have to be perfect • Users can be closely tied to all lifecycle steps • Early and frequent feedback from users • Cumulative costs assessed frequently

31. Spiral Model Weaknesses • Time spent for evaluating risks too large for small or low-risk projects • Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive • The model is complex • Risk assessment expertise is required • Spiral may continue indefinitely • Developers must be reassigned during non-development phase activities • May be hard to define objective, verifiable milestones that indicate readiness to proceed through the next iteration

32. Chapter (2) Information Systems Development Life Cycle Phases

33. The use of a methodology improves the practice of information systems development. A methodology may include: Methodology - A series of phases.- A series of techniques.- A series of tools.- A training scheme.- A philosophy. Method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.

34. Method: Techniques for gathering evidence The various ways of proceeding in gathering information Methodology: The underlying theory and analysis of how research does or should proceed, often influenced by discipline What’s the Difference Between “Method” and “Methodology”?

35. Assessing Methods • Research Question(s) is/are key • Methods must answer the research question(s) • Methodology guides application

36. summary a research methodis a technique for (or way of proceeding in) gathering evidence" methodology is a theory and analysis of how research does or should proceed“

37. Techniques include ways to evaluate the costs and benefits of different solutions and methods to formulate the detailed design necessary to develop computer applications. Techniques Examples:- Flowcharts.- An organization Chart.- Manual documents specification.- Grid chart.- Discussion records.

38. Tools are software packages that aid aspects of information systems development. Tools Examples:- MS Project.- Power designer.- Visio.

39. A Simple System Development Process

40. Systems Development Process Overview

41. System Development Process Overview System initiation – the initial planning for a project to define initial project scope, goals, tasks schedule, and budget. System analysis – the study of a business problem domain to recommend improvements and specify the business requirements and priorities for the solution. System design – the specification or construction of a technical, computer-based solution for the business requirements identified in a system analysis. System implementation – the construction, installation, testing, and delivery of a system into production, provide training for the system users.

42. 1- Initiation (Planning)Phase It involves determining a solid plan for developing your information system. It involves the following three primary activities: 1- define the system to be developed (determine which system is required to support the strategic goals of organization) 2- set the project scope ( it defines the high level system requirements through writing project scope document in one paragraph) 3- develop the project plan ( what , when, and who questions of systems activities to be performed)

43. Chapter (3) System Analysis

44. system analysis It involves end users and IT specialists working together to gather, understand , and document the business requirements for the proposed system through writing (Joint Application Development report) • A requirement is a feature that the system must have or a constraint that it must satisfy to be accepted by the client. • Requirements engineering aims at defining the requirements of the system under construction.

45. Joint Application Development report It is a highly structured workshop that brings together users, managers, and information systems specialists to jointly define and specify user requirements, technical options, and external designs( inputs, outputs, and screen)

46. Joint Application Development report There are numerous of benefits to JAD: 1- it tends to improve the relationship between users, management, and information systems professionals ( increase confidence between user and management) 2- it tends to improve the computer literacy of users and managers as well as the business and application literacy of information systems specialists 3- it places the responsibility for conflict resolution where it belongs 4- it decrease the total system development time by integrating and getting multiple interviews into the structured workshop 5- it lowers the cost of the systems development by getting the requirements correctly defined and prioritized the first time

47. System Analysis Phases Systems analysis consists of three phases: 1- survey project feasibility ( survey phase) 2- study and analyze the current system ( study phase) 3- define and prioritize users’ requirements ( definition phase)

48. System Analysis Phases (survey phase) It answer the question “ is this project worth looking at?” The fundamental objectives of the survey phase are: 1- to identify the problem, opportunities , and ,or directives that initiated this project request 2- to determine if solving the problems exploiting the opportunities, and satisfying the directives will benefit the business

49. System Analysis Phases (survey phase) Survey Phase Activities: 1- Conduct initial interview ( 45-60 minutes) to record lists of people, data, activities, locations and networks, and existing technology, list of problems, opportunities, constraints, ideas, opinions ( fact finding techniques) 2- define the project scope ( of the proposed project through drawing context model that determine the boundaries and scope of the system – data scope- process scope- network scope –function point analysis) 3- classify problems , opportunities, and possible solutions ( a quick fix, enhancement, new development , visibility, priority, and solution in the matrix form) 4- established a proposed project plan 5- present survey findings and recommendations

50. System Analysis Phases (Study phase) It answer the questions: “ are the problems really worth solving?” “ is a new system really worth building?” ( using JAD in one week and one – three day workshop) The fundamental objectives of the study phase are: 1- to understand the business environment of the system 2- to understand the underlying causes and effects of the problems 3- to understand the benefits of exploiting opportunities 4- to understand the implications of noncompliance with directives