Software Lifecycle Models Prepared and presented by Aqeel

Software Lifecycle Models Prepared and presented by Aqeel Ahmed Lecturer UOH

Software System Phases: Vision Definition focus on why focus on what Development Maintenance focus on how focus on change

Software Development Lifecycle Models • A lifecycle model is a series of steps through which the product progresses. • These include • Requirements phase • Specification phase • Design phase • Implementation phase • Integration phase • Maintenance phase • Retirement.

Software Development Lifecycle Models • • Build-and-fix model Waterfall model Rapid prototyping model Incremental model Extreme programming Synchronize-and-stabilize model Spiral model Object-oriented life-cycle models

Build and Fix Model Pros Build First Version 1 Model is simple 2 In this model the product is constructed without specification or any attempt at design. so it is easy. 3 This model may work for small projects. Modified until client is satisfied Cons 1 More effort is required because The developers simply build a product that is reworked as many times as necessary to satisfy the client. 2 It is totally unsatisfactory for products of any reasonable. Maintenanced size. 3 The cost of build-and. Developement fix is actually far greater than the cost of properly specified and carefully designed product. Maintenance 4 Maintenance of the product can be extremely in the absence of any Retirements documentation.

Waterfall Model /linear sequential model What - The systems services, constraints and goals are established by consultation system design users. They arepartitions then defined How – with The system process in detail andtoserve ashardware a system specification. the requirements either of Cons software It establishes and overall No Feed back possiblesystems. in this model. system architecture. Software design involves The fundamental abstractions individualsystem program unit or programs and theirtested relationships. as a complete system to ensure that Normally this is the longest phase of the software requirements have been met. software lifecycle. The system is installed After testing, the software system is delivered and put into practical use. Maintenance to the customer. How – During this stage the software Pros involves correcting errors which were not isinrealized as aphase setofofthe or documents which are approved. 1 design. Result of each isprograms one or more discovered earlier stages life-cycle, units. Unit testing involves 2 program No phase is complete until the documentation for that phase has been completed and improving the implementation of system verifying that phase eachthe unit meets products that have been its approved. units and of enhancing system’s 3 specifications. rarely follow the sequential flow that the model proposes services as. Real newprojects requirements are discovered.

Solution Pros 1 The Waterfall Model is a documentation-driven model that generates complete and comprehensive documentation. 2 Due to complete Documentation the maintenance task become much easier. 3 Feed back is available at each stage for the improvement of each stages. Cons 1 It however suffers from the fact that the client feedback is received when the product is finally delivered and hence any errors in the requirement specification are not discovered until the product is sent to the client after completion. 2 The user requirement can change after long time while final software is delivered to client. 3 The time and cost ultimately goes on wastage if not meet the client satisfaction.

Rapid Prototyping Model used Understanding and capturing of user requirements In Which A mock-up application is created “rapidly” to solicit feedback from the user Once the user requirements are captured in the prototype to the satisfaction of the user A proper requirement specification document is developed and the product is developed from scratch. the internal structure of the rapid prototype is not relevant. Integrating the Waterfall and Rapid Prototyping Models speedup software development process