# Introduction to Software Engineering/Process/Methodology

A software development methodology or system development methodology in software engineering is a framework that is used to structure, plan, and control the process of developing an information system.

## History

The software development methodology framework didn't emerge until the 1960s. According to Elliott (2004) the systems development life cycle (SDLC) can be considered to be the oldest formalized methodology framework for building information systems. The main idea of the SDLC has been "to pursue the development of information systems in a very deliberate, structured and methodical way, requiring each stage of the life cycle from inception of the idea to delivery of the final system, to be carried out in rigidly and sequentially". within the context of the framework being applied. The main target of this methodology framework in the 1960s was "to develop large scale functional business systems in an age of large scale business conglomerates. Information systems activities revolved around heavy data processing and number crunching routines".

### As a noun

As a noun, a software development methodology is a framework that is used to structure, plan, and control the process of developing an information system - this includes the pre-definition of specific deliverables and artifacts that are created and completed by a project team to develop or maintain an application.
A wide variety of such frameworks have evolved over the years, each with its own recognized strengths and weaknesses. One software development methodology framework is not necessarily suitable for use by all projects. Each of the available methodology frameworks are best suited to specific kinds of projects, based on various technical, organizational, project and team considerations.
These software development frameworks are often bound to some kind of organization, which further develops, supports the use, and promotes the methodology framework. The methodology framework is often defined in some kind of formal documentation. Specific software development methodology frameworks (noun) include
* Rational Unified Process (RUP, IBM) since 1998.
* Agile Unified Process (AUP) since 2005 by Scott Ambler

### As a verb

As a verb, the software development methodology is an approach used by organizations and project teams to apply the software development methodology framework (noun). Specific software development methodologies (verb) include:

#### 1970s

* Structured programming since 1969
* Cap Gemini SDM, originally from PANDATA, the first English translation was published in 1974. SDM stands for System Development Methodology

#### 1980s

* Structured Systems Analysis and Design Methodology (SSADM) from 1980 onwards
* Information Requirement Analysis/Soft systems methodology

#### 1990s

* Object-oriented programming (OOP) has been developed since the early 1960s, and developed as a dominant programming approach during the mid-1990s
* Rapid application development (RAD) since 1991
* Scrum, since the late 1990s
* Team software process developed by Watts Humphrey at the SEI
* Extreme Programming since 1999

## Verb approaches

Every software development methodology framework acts as a basis for applying specific approaches to develop and maintain software. Several software development approaches have been used since the origin of information technology. These are:
* Waterfall: a linear framework
* Prototyping: an iterative framework
* Incremental: a combined linear-iterative framework
* Spiral: a combined linear-iterative framework
* Rapid application development (RAD): an iterative framework
* Extreme Programming

### Waterfall development

The Waterfall model is a sequential development approach, in which development is seen as flowing steadily downwards (like a waterfall) through the phases of requirements analysis, design, implementation, testing (validation), integration, and 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:
* Project is divided into sequential phases, with some overlap and splashback acceptable between phases.
* Emphasis is on planning, time schedules, target dates, budgets and implementation of an entire system at one time.
* 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.

### 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:
* Not a standalone, complete development methodology, but rather an approach to handling selected parts of a larger, more traditional development methodology (i.e. incremental, spiral, or rapid application development (RAD)).
* Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process.
* User is involved throughout the development process, which increases the likelihood of user acceptance of the final implementation.
* Small-scale mock-ups of the system are developed following an iterative modification process until the prototype evolves to meet the users’ requirements.
* 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.
* A basic understanding of the fundamental business problem is necessary to avoid solving the wrong problem.

### Incremental development

Various methods are acceptable for combining linear and iterative systems 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:
* 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
* Overall requirements are defined before proceeding to evolutionary, mini-Waterfall development of individual increments of a system, or
* 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.

### Spiral development

The spiral model is a software development process combining elements of both design and prototyping-in-stages, in an effort to combine advantages of top-down and bottom-up concepts.
The basic principles are:
* 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.
* "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."
* Each trip around the spiral traverses four basic quadrants: (1) determine objectives, alternatives, and constraints of the iteration; (2) evaluate alternatives; Identify and resolve risks; (3) develop and verify deliverables from the iteration; and (4) plan the next iteration.
* 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) is a software development methodology, which involves iterative development and the construction of prototypes. Rapid application development is a term originally used to describe a software development process introduced by James Martin in 1991.
The basic principles are:
* Key objective is for fast development and delivery of a high quality system at a relatively low investment cost.
* Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process.
* 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.
* Key emphasis is on fulfilling the business need, while technological or engineering excellence is of lesser importance.
* 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.
* 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.
* Iteratively produces production software, as opposed to a throwaway prototype.
* Produces documentation necessary to facilitate future development and maintenance.
* Standard systems analysis and design methods can be fitted into this framework.

### Other practices

Other methodology practices include:
* Object-oriented development methodologies, such as Grady Booch's object-oriented design (OOD), also known as object-oriented analysis and design (OOAD). The Booch model includes six diagrams: class, object, state transition, interaction, module, and process.
* Top-down programming: evolved in the 1970s by IBM researcher Harlan Mills (and Niklaus Wirth) in developed structured programming.
* 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).
* 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.
* Integrated software development refers to a deliverable based software development framework using the three primary IT (project management, software development, software testing) life cycles that can be leveraged using multiple (iterative, waterfall, spiral, agile) software development approaches, where requirements and solutions evolve via collaboration between self-organizing cross-functional teams.
Software Development Process Evolves Various Processings Hence, software development is not an easy task, it evolves various processings. According to IBM Research: “Software development refers to a set of computer science activities dedicated to the process.
Creating Designing Deploying Supporting Software

## Subtopics
### View model

A view model is framework which provides the viewpoints on the system and its environment, to be used in the software development process. It is a graphical representation of the underlying semantics of a view.
The purpose of viewpoints and views is to enable human engineers to comprehend very complex systems, and to organize the elements of the problem and the solution around domains of expertise. In the engineering of physically intensive systems, viewpoints often correspond to capabilities and responsibilities within the engineering organization.
Most complex system specifications are so extensive that no one individual can fully comprehend all aspects of the specifications. Furthermore, we all have different interests in a given system and different reasons for examining the system's specifications. A business executive will ask different questions of a system make-up than would a system implementer. The concept of viewpoints framework, therefore, is to provide separate viewpoints into the specification of a given complex system. These viewpoints each satisfy an audience with interest in some set of aspects of the system. Associated with each viewpoint is a viewpoint language that optimizes the vocabulary and presentation for the audience of that viewpoint.

### Business process and data modelling

Graphical representation of the current state of information provides a very effective means for presenting information to both users and system developers.
* A business model illustrates the functions associated with the business process being modeled and the organizations that perform these functions. By depicting activities and information flows, a foundation is created to visualize, define, understand, and validate the nature of a process.
* A data model provides the details of information to be stored, and is of primary use when the final product is the generation of computer software code for an application or the preparation of a functional specification to aid a computer software make-or-buy decision. See the figure on the right for an example of the interaction between business process and data models.
Usually, a model is created after conducting an interview, referred to as business analysis. The interview consists of a facilitator asking a series of questions designed to extract required information that describes a process. The interviewer is called a facilitator to emphasize that it is the participants who provide the information. The facilitator should have some knowledge of the process of interest, but this is not as important as having a structured methodology by which the questions are asked of the process expert. The methodology is important because usually a team of facilitators is collecting information across the facility and the results of the information from all the interviewers must fit together once completed.
The models are developed as defining either the current state of the process, in which case the final product is called the "as-is" snapshot model, or a collection of ideas of what the process should contain, resulting in a "what-can-be" model. Generation of process and data models can be used to determine if the existing processes and information systems are sound and only need minor modifications or enhancements, or if re-engineering is required as a corrective action. The creation of business models is more than a way to view or automate your information process. Analysis can be used to fundamentally reshape the way your business or organization conducts its operations.

### Computer-aided software engineering

Computer-aided software engineering (CASE), in the field software engineering is the scientific application of a set of tools and methods to a software which results in high-quality, defect-free, and maintainable software products. It also refers to methods for the development of information systems together with automated tools that can be used in the software development process. The term "computer-aided software engineering" (CASE) can refer to the software used for the automated development of systems software, i.e., computer code. The CASE functions include analysis, design, and programming. CASE tools automate methods for designing, documenting, and producing structured computer code in the desired programming language.
Two key ideas of Computer-aided Software System Engineering (CASE) are:
* Foster computer assistance in software development and or software maintenance processes, and
* An engineering approach to software development and or maintenance.
Typical CASE tools exist for configuration management, data modeling, model transformation, refactoring, source code generation, and Unified Modeling Language.

### Integrated development environment

An integrated development environment (IDE) also known as integrated design environment or integrated debugging environment is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of a:
* source code editor,
* compiler and/or interpreter,
* build automation tools, and
* debugger (usually).
IDEs are designed to maximize programmer productivity by providing tight-knit components with similar user interfaces. Typically an IDE is dedicated to a specific programming language, so as to provide a feature set which most closely matches the programming paradigms of the language.

### Modeling language

A modeling language is any artificial language that can be used to express information or knowledge or systems in a structure that is defined by a consistent set of rules. The rules are used for interpretation of the meaning of components in the structure. A modeling language can be graphical or textual. Graphical modeling languages use a diagram techniques with named symbols that represent concepts and lines that connect the symbols and that represent relationships and various other graphical annotation to represent constraints. Textual modeling languages typically use standardised keywords accompanied by parameters to make computer-interpretable expressions.
Example of graphical modelling languages in the field of software engineering are:
* Business Process Modeling Notation (BPMN, and the XML form BPML) is an example of a process modeling language.
* EXPRESS and EXPRESS-G (ISO 10303-11) is an international standard general-purpose data modeling language.
* Extended Enterprise Modeling Language (EEML) is commonly used for business process modeling across layers.
* Flowchart is a schematic representation of an algorithm or a stepwise process,
* Fundamental Modeling Concepts (FMC) modeling language for software-intensive systems.
* IDEF is a family of modeling languages, the most notable of which include IDEF0 for functional modeling, IDEF1X for information modeling, and IDEF5 for modeling ontologies.
* LePUS3 is an object-oriented visual Design Description Language and a formal specification language that is suitable primarily for modelling large object-oriented (Java, C++, C#) programs and design patterns.
* Specification and Description Language(SDL) is a specification language targeted at the unambiguous specification and description of the behaviour of reactive and distributed systems.
* Unified Modeling Language (UML) is a general-purpose modeling language that is an industry standard for specifying software-intensive systems. UML 2.0, the current version, supports thirteen different diagram techniques, and has widespread tool support.
Not all modeling languages are executable, and for those that are, using them doesn't necessarily mean that programmers are no longer needed. On the contrary, executable modeling languages are intended to amplify the productivity of skilled programmers, so that they can address more difficult problems, such as parallel computing and distributed systems.

### Programming paradigm

A programming paradigm is a fundamental style of computer programming, in contrast to a software engineering methodology, which is a style of solving specific software engineering problems. Paradigms differ in the concepts and abstractions used to represent the elements of a program (such as objects, functions, variables, constraints...) and the steps that compose a computation (assignation, evaluation, continuations, data flows...).
A programming language can support multiple paradigms. For example programs written in C++ or Object Pascal can be purely procedural, or purely object-oriented, or contain elements of both paradigms. Software designers and programmers decide how to use those paradigm elements. In object-oriented programming, programmers can think of a program as a collection of interacting objects, while in functional programming a program can be thought of as a sequence of stateless function evaluations. When programming computers or systems with many processors, process-oriented programming allows programmers to think about applications as sets of concurrent processes acting upon logically shared data structures.
Just as different groups in software engineering advocate different methodologies, different programming languages advocate different programming paradigms. Some languages are designed to support one paradigm (Smalltalk supports object-oriented programming, Haskell supports functional programming), while other programming languages support multiple paradigms (such as Object Pascal, C++, C#, Visual Basic, Common Lisp, Scheme, Python, Ruby, and Oz).
Many programming paradigms are as well known for what methods they forbid as for what they enable. For instance, pure functional programming forbids using side-effects; structured programming forbids using goto statements. Partly for this reason, new paradigms are often regarded as doctrinaire or overly rigid by those accustomed to earlier styles. Avoiding certain methods can make it easier to prove theorems about a program's correctness, or simply to understand its behavior.

### Software framework

A software framework is a re-usable design for a software system or subsystem. A software framework may include support programs, code libraries, a scripting language, or other software to help develop and glue together the different components of a software project. Various parts of the framework may be exposed via an API.

### Software development process

A software development process is a framework imposed on the development of a software product. Synonyms include software life cycle and software process. There are several models for such processes, each describing approaches to a variety of tasks or activities that take place during the process.
A largely growing body of software development organizations implement process methodologies. Many of them are in the defense industry, which in the U.S. requires a rating based on 'process models' to obtain contracts. The international standard describing the method to select, implement and monitor the life cycle for software is ISO 12207.
A decades-long goal has been to find repeatable, predictable processes that improve productivity and quality. Some try to systematize or formalize the seemingly unruly task of writing software. Others apply project management methods to writing software. Without project management, software projects can easily be delivered late or over budget. With large numbers of software projects not meeting their expectations in terms of functionality, cost, or delivery schedule, effective project management appears to be lacking.

## See also
### Lists

* List of software engineering topics
* List of software development philosophies

### Related topics

* Domain-specific modeling
* Lightweight methodology
* Object modeling language
* Structured programming
* Integrated IT Methodology

## References

* 1 2 Geoffrey Elliott (2004) Global Business Information Technology: an integrated systems approach. Pearson Education. p.87.
* 1 2 3 4 5 6 7 8 Centers for Medicare & Medicaid Services (CMS) Office of Information Service (2008). Selecting a development approach. Webarticle. United States Department of Health and Human Services (HHS). Revalidated: March 27, 2008. Retrieved 15 July 2015.
* ↑ Wasserfallmodell > Entstehungskontext, Markus Rerych, Institut für Gestaltungs- und Wirkungsforschung, TU-Wien. Accessed on line November 28, 2007.
* 1 2 Barry Boehm (1996., "A Spiral Model of Software Development and Enhancement". In: ACM SIGSOFT Software Engineering Notes (ACM) 11(4):14-24, August 1986
* ↑ Richard H. Thayer, Barry W. Boehm (1986). Tutorial: software engineering project management. Computer Society Press of the IEEE. p.130
* ↑ Barry W. Boehm (2000). Software cost estimation with Cocomo II: Volume 1.
* ↑ Georges Gauthier Merx & Ronald J. Norman (2006). Unified Software Engineering with Java. p.201.
* ↑ Edward J. Barkmeyer ea (2003). Concepts for Automating Systems Integration NIST 2003.
* 1 2 3 4 Paul R. Smith & Richard Sarfaty (1993). Creating a strategic plan for configuration management using Computer Aided Software Engineering (CASE) tools. Paper For 1993 National DOE/Contractors and Facilities CAD/CAE User's Group.
* ↑ Kuhn, D.L (1989). "Selecting and effectively using a computer aided software engineering tool". Annual Westinghouse computer symposium; 6-7 Nov 1989; Pittsburgh, PA (USA); DOE Project.
* ↑ P. Loucopoulos and V. Karakostas (1995). System Requirements Engineering. McGraw-Hill.
* ↑ CASE definition In: Telecom Glossary 2000. Retrieved 26 Oct 2008.
* ↑ K. Robinson (1992). Putting the Software Engineering into CASE. New York : John Wiley and Sons Inc.
* ↑ Xiao He (2007). "A metamodel for the notation of graphical modeling languages". In: Computer Software and Applications Conference, 2007. COMPSAC 2007 - Vol. 1. 31st Annual International, Volume 1, Issue , 24–27 July 2007, pp 219-224.

## External links

* Selecting a development approach at cms.gov.
* Software Methodologies Book Reviews An extensive set of book reviews related to software methodologies and processes