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Phased life cycle model

The waterfall model segments the software development process into sequential phases: planning, requirements definition, design, implementation, system testing, and maintenance. Each phase has defined inputs, processes, and outputs. The planning phase involves understanding the problem, feasibility studies, and developing a solution. Requirements definition produces a specification describing the required software functions and constraints. Design identifies software components and their relationships. Implementation translates the design into code. System testing integrates and accepts the software. Maintenance modifies the software after release. While the phases are linear, the development process is not always perfectly sequential.

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Software Engineering•
Prepared by R.Nancy Beaulah
 Segments the software life cycles in to series of successive activities.  Each phase requires  Well defined input information  Well defined processes  Well defined products  Resources are needed for each phase  Each phase utilizes explicit methods, tools and techniques
Analysis Design Implementation SystemTesting Maintenance Sometimes it is called as Water Fall Chart
 Consist of two phases ▪ Planning ▪ Requirements Definition  Activities of Planning ▪ Understanding the Problem ▪ Perform a feasibility study ▪ Developing a solution ▪ Determine acceptance criteria ▪ Planning the development process
 Products ▪ System definition ▪ Project plan  System definition ▪ Expressed in English or in any natural language ▪ May use charts, figures, graphs, tables and equations ▪ Notations used depend upon the problem  Project plan ▪ Life cycle model to be used ▪ Organizational structure
▪ Preliminary development schedule ▪ Preliminary cost schedule ▪ Preliminary resource schedule ▪ Preliminary staffing schedule ▪ Tools and techniques used  Time and cost are basically calculated because it is not possible to estimate exactly without doing basic design.
 PreliminaryCost Estimate – Planning Stage  Refined Cost Estimate – Preliminary Design Review  FinalCost Estimate – Critical Design Review  Requirements Definition  It includes basic functions of software components in hardware, software, and people subsystem.
 The product of requirements definition  The product of requirements definition is a specification that describes ▪ The processing environment ▪ The required software functions. ▪ Performance constraints on the software. ▪ Exception handling ▪ Acceptance criteria
 Design phase:  In the phased model, software design follows analysis  Design phase identified software components 1. Functions. 2. Data streams 3. Data stores  It specifies relationship among components.  It specifies software structures.  Maintains a record of design decision.  Blueprint for the implementation phase.
 Design phase consist of 1. Architectural design 2. Detailed design  Architectural design:  It involves identifying the software components dividing them into software modules and conceptual data structures, specifying interconnection among components.
 Detailed design  It is concerned with the details of “how to” ▪ Package the processing modules. ▪ Implement the processing, algorithm, data structures and interconnection among modules.
 Implementation phase:  It involves translation of design specification into source code and debugging, documentation and unit testing of source code.  Errors:  Implementation phase may include errors in routines, functions, logical errors,and algorithm, errors in data structure layout.
 System testing:  It involves 2 kinds of activities ▪ 1. Integration testing ▪ 2. Acceptance testing  Integration testing:  Developing a strategy for integrating the software components into a function requires careful planning so that modules are available for integration when needed.
 Acceptance testing:  It involves planning an execution of various type of test that software system satisfied requirements documents.  After getting the acceptance from the customer software system of released for production work and maintenance phase.
 Maintenance Phase:  It Includes ▪ the enhancement of capabilities. ▪ Adaptation of software to new processing environment. ▪ correction of software bugs.
 Phases are Linear  Development Process is not Linear  Development activities never proceed as in water fall chart  Only possible when it is possible to specify everything at the beginning itself  Suitable for developers who developed similar systems
 Software EngineeringConcepts, Richard Fairley