Lecture Hand notes on SDLC, Lecture notes of Software Development

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Software Development Lifecycles

Instructor: Samir Pokharel

Importance

• (^) Requirements collection can be incomplete or

not deep enough.

• (^) The lack of methodical, quantifiable methods

drives to difficult situations.

• (^) The lack of systematic methods drive to weak

or too complex architecture.

• (^) Difficult to change.
• (^) Code will become not easy to maintain. SDLC_1 2

Software Development Lifecycles

SDLC_1 4

Process Model

• (^) A process model is a description of the sequence of activities carried out in an SE project, and the relative order of these activities.
• (^) It provides a fixed generic framework that can be tailored to a specific project.
• (^) A software process model is an abstract representation of a process that presents a description of a process from some particular perspective.

Personal Process Model

• (^) This model is good from the perspective that an individual software engineer can use it to improve his or her personal productivity and work on product quality.
• (^) It defines five framework activities: planning, high-level design, high-level design review, development, and postmortem.
• (^) It stresses the need to identify errors early and to understand the types of errors.

Personal Process Model

• (^) Planning : it isolates requirements and a project schedule is created.
• (^) High-level design : Prototypes are built.
• (^) High-level design review : Formal verification methods are applied to uncover errors in the design.
• (^) Development : Code is generated, reviewed, compiled, and tested.
• (^) Postmortem: using the measures and metrics collected, the effectiveness of the process is determined.

Team Process Model

• (^) is a software development process for

engineering team and goal is to build a “self-

directed” project team that organizes itself to

produce high-quality s/w.

• (^) is intended to improve the levels of quality and

productivity of a team's software development

project, in order to help them better meet the

cost and schedule commitments of developing

a software system

Predictive vs Adaptive model…

SDLC_1 11

Waterfall Model

Waterfall Model

• (^) first Process Model and it is also referred to as a linear-sequential life cycle model.
• (^) very simple to understand and use.
• (^) each phase must be completed fully before the next phase can begin.
• (^) basically used for the for the project which is small and there are no uncertain requirements.
• (^) At the end of each phase, a review takes place to determine if the project is on the right path and whether or not to continue or discard the project.
• (^) In this model the testing starts only after the development is complete.
• (^) In waterfall model phases do not overlap.

Disadvantages

• (^) Once an application is in the testing stage, it is very difficult to go back and change something that was not well-thought out in the concept stage.
• (^) No working software is produced until late during the life cycle.
• (^) High amounts of risk and uncertainty.
• (^) Not a good model for complex and object-oriented projects.
• (^) Poor model for long and ongoing projects.
• (^) Not suitable for the projects where requirements are at a moderate to high risk of changing.

When to use?

• (^) This model is used only when the requirements are very well known, clear and fixed.
• (^) Product definition is stable.
• (^) Technology is understood.
• (^) There are no ambiguous requirements
• (^) Ample resources with required expertise are available freely
• (^) The project is short.

Incremental Models

• (^) the whole requirement is divided into various builds so multiple development cycles take place here, making the life cycle a “multi-waterfall” cycle.
• (^) Cycles are divided up into smaller, more easily managed modules and each module passes through the requirements, design, implementation and testing phases.
• (^) A working version of software is produced during the first module, so you have working software early on during the software life cycle.
• (^) Each subsequent release of the module adds function to the previous release and the process continues till the complete system is achieved.

Advantages

• (^) Generates working software quickly and early during the software life cycle.
• (^) This model is more flexible – less costly to change scope and requirements.
• (^) It is easier to test and debug during a smaller iteration.
• (^) In this model customer can respond to each built.
• (^) Lowers initial delivery cost.
• (^) Easier to manage risk because risky pieces are identified and handled during it’d iteration.