Approaches to system development

1. Approaches to system development

2. Lecturer details • Systems Development Life Cycle • Phases and Activities in the SDLC • Variations of the SDLC models

3. System development life cycle (SDLC) • SDLCProvides overall framework for managing systems development process • Two main approaches to SDLC • Predictive approach – assumes project can be planned out in advance • Adaptive approach – more flexible, assumes project cannot be planned out in advance

4. Stages of SDLC • Project planning – initiate, ensure feasibility, plan schedule, obtain approval for project • Analysis– understand business needs and processing requirements • Design – define solution system based on requirements and analysis decisions • Implementation – construct, test, train users, and install new system • Support– keep system running and improve

5. Stage 1&2: Project planning/Analysis • Define business problem and scope • Produce detailed project schedule • Confirm project feasibility / • - Economic, organizational, technical, resource, and schedule • Staff the project (resource management)‏ • Launch project  official announcement • --------------------------------------------------------------------------------- • Gather information to learn problem domain • Define system requirements • Build prototypes for discovery of requirements • Prioritize requirements • Generate and evaluate alternatives • Review recommendations with management

6. Stage 3&4: Project design/ Implementation • Design and integrate the network • Design the application architecture • Design the user interfaces • Design the system interfaces • Design and integrate the database • Prototype for design details • Design and integrate system controls • --------------------------------------------------------------------------------- • Construct software components • Verify and test • Convert data • Train users and document the system • Install the system

7. Stage 5: Support • Maintain system • Small patches, repairs, and updates • Enhance system • Small upgrades or enhancements to expand system capabilities • Larger enhancements may require separate development project • Support users • Help desk and/or support team

8. SDLC approaches: Waterfall (1) • Each life cycle phase is completed in sequence • No going back once the phase is completed (like a waterfall) • The key deliverables are typically produced on paper (hundreds of pages in length) • The decisions made at each phase are frozen

9. Waterfall model pros and cons The two key advantages of the waterfall model: • Identifying system requirements long before programming begins • It minimizes changes to the requirements as the project proceeds The key disadvantages: • The design must be completely specified on paper before programming begins • A paper document is often a poor communication mechanism, so important requirements can be overlooked in the hundreds of pages of documentation • Users rarely are prepared for their introduction to the new system, which occurs long after the initial idea for the system was introduced. • A system may require significant rework because of changes in business environment since the time the analysis phase occurred

10. Overlaps of Activities

11. SDLC approaches: Parallel Model (2) • TheParallel Model is doing the design and implementation in sequence, it performs a general design for the whole system • It then divides the project into series of distinct subprojects that can be designed and implemented in parallel • Once all subprojects are complete, the final integration of the separate pieces is delivered

12. Parallel model pros and cons Primary advantages: • Can reduce the schedule time required to deliver a system • There is less chance of changes in the business environment causing rework • Key disadvantages: • Still suffers from problems caused by paper documentation • A new problem: sometimes the subprojects are not completely independent; design made in one subproject may affect another and the end of the project may require significant integrative efforts

13. SDLC approaches: Spiral model (3) • Project cycles through development activities over and over until project is complete • Prototype created by end of each cycle • Focuses on mitigating risk

15. SDLC approaches: Iteration model (4) • Iteration: the process of looping through the same development activities multiple times, sometimes at increasing levels of details or accuracy • Assumes no one gets the right results the first time (version) • Do some analysis, then some design, then some implementation, then do some further analysis, etc until you get it right • the amount of iteration depends on the complexity of the project.

17. SDLC approaches: Phased model (5) • Breaks the overall system into a series of versions that are developed sequentially • The analysis phase identifies the overall system concept. The project team, users and system sponsors categorize the requirements into a series of versions • The most important and fundamental requirements are bundled into the first version of the system.

18. Pros and cons of Phased model • Advantages: • Quickly getting a useful system into the hands of users. Although it does not perform all the functions the users need, it helps them sooner to identify important additional requirements • Disadvantages: • The users begin to work with systems that are incomplete. It is critical to identify the most important and useful features and include them in the first version. 

19. SDLC approaches: Prototyping model (6) • Performs analysis, design and implementation phases concurrently, • All three phases are performed repeatedly in a cycle until the system is completed. • The basics of analysis and design are performed, and work immediately begins on a system prototype

20. Prototyping model pros and cons The key advantages: • Very quickly provides a system for users to interact with. It reassures the users that the project team is working on the system. • The users can interact with the prototype to better understanding what it can and cannot do rather than attempting to understand a system specification on paper. The major disadvantages: • Fast-paced system releases challenge attempts to conduct careful, methodical analysis. Often the prototype undergoes such significant changes that many initial design decisions become poor ones

21. End Thank you ??????