PCBizness Technosoft Pvt. Ltd. In software engineering, a software development methodology (also known as a system development methodology, software development life cycle, software development process, software process) is a division of software development work into distinct phases (or stages) containing activities with the intent of better planning and management. It is often considered a subset of the systems development life cycle. The methodology may include the pre-definition of specific deliverables and artifacts that are created and completed by a project team to develop or maintain an application. Common methodologies include waterfall, prototyping, iterative and incremental development, spiral development, rapid application development, extreme programming and agile methodology. Some people consider a life-cycle model a more general term for a category of methodologies and a software development process a more specific term to refer to a specific process chosen by a specific organization. For example, there are many specific software development processes that fit the spiral life-cycle model. Approaches:- Several software development approaches have been used since the origin of information technology, in two main categories. Typically an approach or a combination of approaches is chosen by management or a development team. Traditional methodologies such as waterfall that have distinct phases are sometimes known as software development life cycle (SDLC) methodologies, though this term could also be used more generally to refer to any methodology. A life cycle approach with distinct phases is in contrast to Agile approaches which define a process of iteration, but where design, construction, and deployment of different pieces can occur simultaneously. Waterfall development The activities of the software development process represented in the waterfall model. There are several other models to represent this process. The waterfall model is a sequential development approach, in which development is seen as flowing steadily downwards (like a waterfall) through several phases, typically: 1. Requirements analysis resulting in a software requirements specification 2. Software design 3. Implementation 4. Testing 5. Integration, if there are multiple subsystems 6. Deployment (or Installation) 7. Maintenance The first formal description of the method is often cited as an article published by Winston W. Royce in 1970 although Royce did not use the term waterfall in this article. The basic principles are 1. Project is divided into sequential phases, with some overlap and splashback acceptable between phases. 2. Emphasis is on planning, time schedules, target dates, budgets and implementation of an entire system at one time. 3. Tight control is maintained over the life of the project via extensive written documentation, formal reviews, and approval/signoff by the user and information technology management occurring at the end of most phases before beginning the next phase. The waterfall model is a traditional engineering approach applied to software engineering. A strict waterfall approach discourages revisiting and revising any prior phase once it is complete. This inflexibility in a pure waterfall model has been a source of criticism by supporters of other more flexible models. It has been widely blamed for several large-scale government projects running over budget, over time and sometimes failing to deliver on requirements due to the Big Design Up Front approach. Except when contractually required, the waterfall model has been largely superseded by more flexible and versatile methodologies developed specifically for software development. See Criticism of Waterfall model. The waterfall model is also commonly taught with the mnemonic A Dance in the Dark Every Monday, representing Analysis, Design, Implementation, Testing, Documentation and Execution, and Maintenance. Prototyping Software prototyping, is the development approach of activities during software development, the creation of prototypes, i.e., incomplete versions of the software program being developed. The basic principles are: 1. Not a standalone, complete development methodology, but rather an approach to handle selected parts of a larger, more traditional development methodology (i.e. incremental, spiral, or rapid application development (RAD)). 2. Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process. 3. User is involved throughout the development process, which increases the likelihood of user acceptance of the final implementation. 4. Small-scale mock-ups of the system are developed following an iterative modification process until the prototype evolves to meet the users’ requirements. 5. While most prototypes are developed with the expectation that they will be discarded, it is possible in some cases to evolve from prototype to working system. 6. A basic understanding of the fundamental business problem is necessary to avoid solving the wrong problems. Incremental development Various methods are acceptable for combining linear and iterative software development methodologies, with the primary objective of each being to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process. The basic principles are: 1. A series of mini-Waterfalls are performed, where all phases of the Waterfall are completed for a small part of a system, before proceeding to the next increment, or 2. Overall requirements are defined before proceeding to evolutionary, mini-Waterfall development of individual increments of a system, or 3. The initial software concept, requirements analysis, and design of architecture and system core are defined via Waterfall, followed by iterative Prototyping, which culminates in installing the final prototype, a working system . Iterative and incremental development Main article: Iterative and incremental development Iterative development prescribes the construction of initially small but ever-larger portions of a software project to help all those involved to uncover important issues early before problems or faulty assumptions can lead to disaster. Spiral development Spiral model (Boehm, 1988) In 1988, Barry Boehm published a formal software development spiral model, which combines some key aspect of the waterfall model and rapid prototyping methodologies, in an effort to combine advantages of top-down and bottom-up concepts. It provided emphasis in a key area many felt had been neglected by other methodologies: deliberate iterative risk analysis, particularly suited to large-scale complex systems. The basic principles are: 1. Focus is on risk assessment and on minimizing project risk by breaking a project into smaller segments and providing more ease-of-change during the development process, as well as providing the opportunity to evaluate risks and weigh consideration of project continuation throughout the life cycle. 2. Each cycle involves a progression through the same sequence of steps, for each part of the product and for each of its levels of elaboration, from an overall concept-of-operation document down to the coding of each individual program. 3. Each trip around the spiral traverses four basic quadrants: determine objectives, alternatives, and constraints of the iteration; evaluate alternatives; Identify and resolve risks; develop and verify deliverables from the iteration; and plan the next iteration. 4. Begin each cycle with an identification of stakeholders and their win conditions, and end each cycle with review and commitment. Rapid application development Rapid Application Development (RAD) Model Rapid application development (RAD) is a software development methodology, which favors iterative development and the rapid construction of prototypes instead of large amounts of up-front planning. The planning of software developed using RAD is interleaved with writing the software itself. The lack of extensive pre-planning generally allows software to be written much faster, and makes it easier to change requirements. The rapid development process starts with the development of preliminary data models and business process models using structured techniques. In the next stage, requirements are verified using prototyping, eventually to refine the data and process models. These stages are repeated iteratively; further development results in a combined business requirements and technical design statement to be used for constructing new systems. The term was first used to describe a software development process introduced by James Martin in 1991. According to Whitten (2003), it is a merger of various structured techniques, especially data-driven Information Engineering, with prototyping techniques to accelerate software systems development. The basic principles of rapid application development are: 1. Key objective is for fast development and delivery of a high quality system at a relatively low investment cost. 2. Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process. 3. Aims to produce high quality systems quickly, primarily via iterative Prototyping (at any stage of development), active user involvement, and computerized development tools. These tools may include Graphical User Interface (GUI) builders, Computer Aided Software Engineering (CASE) tools, Database Management Systems (DBMS), fourth-generation programming languages, code generators, and object-oriented techniques. 4. Key emphasis is on fulfilling the business need, while technological or engineering excellence is of lesser importance. 5. Project control involves prioritizing development and defining delivery deadlines or “timeboxes”. If the project starts to slip, emphasis is on reducing requirements to fit the timebox, not in increasing the deadline. 6. Generally includes joint application design (JAD), where users are intensely involved in system design, via consensus building in either structured workshops, or electronically facilitated interaction. Active user involvement is imperative. 7. Iteratively produces production software, as opposed to a throwaway prototype. 8. Produces documentation necessary to facilitate future development and maintenance. 9. Standard systems analysis and design methods can be fitted into this framework. Agile development Agile software development refers to a group of software development methodologies based on iterative development, where requirements and solutions evolve via collaboration between self-organizing cross-functional teams. The term was coined in the year 2001 when the Agile Manifesto was formulated. Agile software development uses iterative development as a basis but advocates a lighter and more people-centric viewpoint than traditional approaches. Agile processes fundamentally incorporate iteration and the continuous feedback that it provides to successively refine and deliver a software system. There are many variations of agile processes: 1. Dynamic systems development method (DSDM) 2. Kanban 3. Scrum 4. Code and fix 5. Main article: Cowboy coding Code and fix development is not so much a deliberate strategy as an artifact of naïveté and schedule pressure on software developers. Without much of a design in the way, programmers immediately begin producing code. At some point, testing begins (often late in the development cycle), and the unavoidable bugs must then be fixed before the product can be shipped. Programming without a planned-out design is also known as cowboy coding. Lightweight methodologies A lightweight methodology has a small number of rules. Some of these methodologies are also considered agile. Adaptive Software Development by Jim Highsmith, described in his 1999 book Adaptive Software Development Crystal Clear family of methodologies with Alistair Cockburn, Extreme Programming (XP), promoted by people such as Kent Beck and Martin Fowler. In extreme programming, the phases are carried out in extremely small (or continuous) steps compared to the older, batch processes. The (intentionally incomplete) first pass through the steps might take a day or a week, rather than the months or years of each complete step in the Waterfall model. First, one writes automated tests, to provide concrete goals for software development. Next is coding (by programmers working in pairs, a technique known as pair programming), which is complete when all the tests pass, and the programmers cant think of any more tests that are needed. Design and architecture emerge from refactoring, and come after coding. The same people who do the coding do design. (Only the last feature — merging design and code — is common to all the other agile processes.) The incomplete but functional system is deployed or demonstrated for (some subset of) the users (at least one of which is on the development team). At this point, the practitioners start again on writing tests for the next most important part of the system. Feature Driven Development (FDD) developed (1999) by Jeff De Luca and Peter Coad ICONIX - UML-based object modeling with use cases, a lightweight precursor to the Rational Unified Process Other high-level software project methodologies include: Chaos model - The main rule is always resolve the most important issue first. Incremental funding methodology - an iterative approach Structured systems analysis and design method - a specific version of waterfall Slow programming, as part of the larger Slow Movement, emphasizes careful and gradual work without (or minimal) time pressures. Slow programming aims to avoid bugs and overly quick release schedules. V-Model (software development) - an extension of the waterfall model Unified Process (UP) is an iterative software development methodology framework, based on Unified Modeling Language (UML). UP organizes the development of software into four phases, each consisting of one or more executable iterations of the software at that stage of development: inception, elaboration, construction, and guidelines. Many tools and products exist to facilitate UP implementation. One of the more popular versions of UP is the Rational Unified Process (RUP). for more details:jasleensoftwaredevelopment.blogspot/2015/01/software-developement-process.html
Posted on: Mon, 05 Jan 2015 04:43:27 +0000
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