software design software development core activities processes requirements design engineering construction testing debugging deployment maintenance paradigms and models agile cleanroom incremental prototyping spiral v model waterfall methodologies and frameworks asd devops dad dsdm fdd iid kanban lean sd less mdd msf psp rad rup safe scrum semat tsp up xp supporting disciplines configuration management documentation software quality assurance sqa project management user experience practices atdd bdd cco ci cd ddd pp standup tdd tools compiler debugger profiler gui designer modeling ide build automation release automation infrastructure as code testing standards and bodies of knowledge babok cmmi ieee standards iso 9001 isoiec standards pmbok swebok itil glossaries artificial intelligence computer science electrical and electronics engineering vte software design is the process by which an agent creates a specification of a software artifact intended to accomplish goals using a set of primitive components and subject to constraints software design usually involves problem solving and planning a software solution this includes both a lowlevel component and algorithm design and a highlevel architecture design overview software design is the process of envisioning and defining software solutions to one or more sets of problems one of the main components of software design is the software requirements analysis sra sra is a part of the software development process that lists specifications used in software engineering if the software is semiautomated or user centered software design may involve user experience design yielding a storyboard to help determine those specifications if the software is completely automated meaning no user or user interface a software design may be as simple as a flow chart or text describing a planned sequence of events there are also semistandard methods like unified modeling language and fundamental modeling concepts in either case some documentation of the plan is usually the product of the design furthermore a software design may be platformindependent or platformspecific depending upon the availability of the technology used for the design the main difference between software analysis and design is that the output of a software analysis consists of smaller problems to solve additionally the analysis should not be designed very differently across different team members or groups in contrast the design focuses on capabilities and thus multiple designs for the same problem can and will exist depending on the environment the design often varies whether it is created from reliable frameworks or implemented with suitable design patterns design examples include operation systems webpages mobile devices or even the new cloud computing paradigm software design is both a process and a model the design process is a sequence of steps that enables the designer to describe all aspects of the software for building creative skill past experience a sense of what makes good software and an overall commitment to quality are examples of critical success factors for a competent design it is important to note however that the design process is not always a straightforward procedure the design model can be compared to an architects plans for a house it begins by representing the totality of the thing that is to be built eg a threedimensional rendering of the house slowly the thing is refined to provide guidance for constructing each detail eg the plumbing lay similarly the design model that is created for software provides a variety of different views of the computer software basic design principles enable the software engineer to navigate the design process davis suggests a set of principles for software design which have been adapted and extended in the following list the design process should not suffer from tunnel vision a good designer should consider alternative approaches judging each based on the requirements of the problem the resources available to do the job the design should be traceable to the analysis model because a single element of the design model can often be traced back to multiple requirements it is necessary to have a means for tracking how requirements have been satisfied by the design model the design should not reinvent the wheel systems are constructed using a set of design patterns many of which have likely been encountered before these patterns should always be chosen as an alternative to reinvention time is short and resources are limited design time should be invested in representing truly new ideas by integrating patterns that already exist when applicable the design should minimize the intellectual distance between the software and the problem as it exists in the real world that is the structure of the software design should whenever possible mimic the structure of the problem domain the design should exhibit uniformity and integration a design is uniform if it appears fully coherent in order to achieve this outcome rules of style and format should be defined for a design team before design work begins a design is integrated if care is taken in defining interfaces between design components the design should be structured to accommodate change the design concepts discussed in the next section enable a design to achieve this principle the design should be structured to degrade gently even when aberrant data events or operating conditions are encountered well designed software should never bomb it should be designed to accommodate unusual circumstances and if it must terminate processing it should do so in a graceful manner design is not coding coding is not design even when detailed procedural designs are created for program components the level of abstraction of the design model is higher than the source code the only design decisions made at the coding level should address the small implementation details that enable the procedural design to be coded the design should be assessed for quality as it is being created not after the fact a variety of design concepts and design measures are available to assist the designer in assessing quality throughout the development process the design should be reviewed to minimize conceptual semantic errors there is sometimes a tendency to focus on minutiae when the design is reviewed missing the forest for the trees a design team should ensure that major conceptual elements of the design omissions ambiguity inconsistency have been addressed before worrying about the syntax of the design model design concepts the design concepts provide the software designer with a foundation from which more sophisticated methods can be applied a set of fundamental design concepts has evolved they are as follows abstraction abstraction is the process or result of generalization by reducing the information content of a concept or an observable phenomenon typically in order to retain only information which is relevant for a particular purposeit is an act of representing essential features without including the background details or explanations refinement it is the process of elaboration a hierarchy is developed by decomposing a macroscopic statement of function in a stepwise fashion until programming language statements are reached in each step one or several instructions of a given program are decomposed into more detailed instructions abstraction and refinement are complementary concepts modularity software architecture is divided into components called modules software architecture it refers to the overall structure of the software and the ways in which that structure provides conceptual integrity for a system good software architecture will yield a good return on investment with respect to the desired outcome of the project eg in terms of performance quality schedule and cost control hierarchy a program structure that represents the organization of a program component and implies a hierarchy of control structural partitioning the program structure can be divided into both horizontally and vertically horizontal partitions define separate branches of modular hierarchy for each major program function vertical partitioning suggests that control and work should be distributed top down in the program structure data structure it is a representation of the logical relationship among individual elements of data software procedure it focuses on the processing of each module individually information hiding modules should be specified and designed so that information contained within a module is inaccessible to other modules that have no need for such information in his object model grady booch mentions abstraction encapsulation modularisation and hierarchy as fundamental software design principles design considerations there are many aspects to consider in the design of a piece of software the importance of each consideration should reflect the goals and expectations that the software is being created to meet some of these aspects are compatibility the software is able to operate with other products that are designed for interoperability with another product for example a piece of software may be backwardcompatible with an older version of itself extensibility new capabilities can be added to the software without major changes to the underlying architecture modularity the resulting software comprises well defined independent components which leads to better maintainability the components could be then implemented and tested in isolation before being integrated to form a desired software system this allows division of work in a software development project faulttolerance the software is resistant to and able to recover from component failure maintainability a measure of how easily bug fixes or functional modifications can be accomplished high maintainability can be the product of modularity and extensibility reliability software durability the software is able to perform a required function under stated conditions for a specified period of time reusability the ability to use some or all of the aspects of the preexisting software in other projects with little to no modification robustness the software is able to operate under stress or tolerate unpredictable or invalid input for example it can be designed with resilience to low memory conditions security the software is able to withstand and resist hostile acts and influences usability the software user interface must be usable for its target useraudience default values for the parameters must be chosen so that they are a good choice for the majority of the users performance the software performs its tasks within a timeframe that is acceptable for the user and does not require too much memory portability the software should be usable across a number of different conditions and environments scalability the software adapts well to increasing data or number of users modeling language a modeling language is any artificial language that can be used to express information knowledge or systems in a structure that is defined by a consistent set of rules these rules are used for interpretation of the components within the structure a modeling language can be graphical or textual examples of graphical modeling languages for software design are architecture description language adl is a language used to describe and represent the software architecture of a software system business process modeling notation bpmn is an example of a process modeling language express and expressg iso 1030311 is an international standard generalpurpose data modeling language extended enterprise modeling language eeml is commonly used for business process modeling across a number of layers flowchart is a schematic representation of an algorithm or stepwise process fundamental modeling concepts fmc is modeling language for softwareintensive 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 jackson structured programming jsp is a method for structured programming based on correspondences between data stream structure and program structure lepus3 is an objectoriented visual design description language and a formal specification language that is suitable primarily for modeling large objectoriented java c c programs and design patterns unified modeling language uml is a general modeling language to describe software both structurally and behaviorally it has a graphical notation and allows for extension with a profile uml alloy specification language is a general purpose specification language for expressing complex structural constraints and behavior in a software system it provides a concise language base on firstorder relational logic systems modeling language sysml is a new generalpurpose modeling language for systems engineering serviceoriented modeling framework somf design patterns a software designer or architect may identify a design problem which has been visited and perhaps even solved by others in the past a template or pattern describing a solution to a common problem is known as a design pattern the reuse of such patterns can help speed up the software development process technique the difficulty of using the term design in relation to software is that in some senses the source code of a program is the design for the program that it produces to the extent that this is true software design refers to the design of the design edsger w dijkstra referred to this layering of semantic levels as the radical novelty of computer programming and donald knuth used his experience writing tex to describe the futility of attempting to design a program prior to implementing it mwparseroutput templatequoteoverflowhiddenmargin1em 0padding0 40pxmwparseroutput templatequote templatequotecitelineheight15emtextalignleftpaddingleft16emmargintop0 tex would have been a complete failure if i had merely specified it and not participated fully in its initial implementation the process of implementation constantly led me to unanticipated questions and to new insights about how the original specifications could be improved usage software design documentation may be reviewed or presented to allow constraints specifications and even requirements to be adjusted prior to computer programming redesign may occur after review of a programmed simulation or prototype it is possible to design software in the process of programming without a plan or requirement analysis but for more complex projects this would not be considered feasible a separate design prior to programming allows for multidisciplinary designers and subject matter experts smes to collaborate with highly skilled programmers for software that is both useful and technically sound wikimedia commons has media related to software design aspectoriented software development bachelor of science in information technology design rationale interaction design icon design searchbased software engineering software design description ieee 1016 software development user experience user interface design zero one infinity roger s pressman software engineering a practitioners approach mcgrawhill isbn0073655783 vtemajor fields of computer sciencenote this template roughly follows the 2012 acm computing classification systemhardware printed circuit board peripheral integrated circuit very large scale integration systems on chip socs energy consumption green computing electronic design automation hardware acceleration computer systemsorganization computer architecture embedded system realtime computing dependability networks network architecture network protocol network components network scheduler network performance evaluation network service software organization interpreter middleware virtual machine operating system software quality software notationsand tools programming paradigm programming language compiler domainspecific language modeling language software framework integrated development environment software configuration management software library software repository software development software development process requirements analysis software design software construction software deployment software maintenance programming team opensource model theory of computation model of computation formal language automata theory computational complexity theory logic semantics algorithms algorithm design analysis of algorithms algorithmic efficiency randomized algorithm computational geometry mathematicsof computing discrete mathematics probability statistics mathematical software information theory mathematical analysis numerical analysis informationsystems database management system information storage systems enterprise information system social information systems geographic 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software verification and validation structured analysis orientations agile aspectoriented object orientation ontology service orientation sdlc modelsdevelopmental agile eup executable uml incremental model iterative model prototype model rad up scrum spiral model vmodel waterfall model xp other spice cmmi data model er model function model information model metamodeling object model systems model view model languages idef uml usl sysml softwareengineers victor basili kent beck grady booch fred brooks barry boehm peter chen danese cooper ward cunningham tom demarco edsger w dijkstra delores m etter martin fowler adele goldstine margaret hamilton c a r hoare lois haibt mary jean harrold grace hopper watts humphrey michael a jackson ivar jacobson alan kay nancy leveson stephen j mellor bertrand meyer david parnas trygve reenskaug winston w royce james rumbaugh mary shaw peri tarr elaine weyuker niklaus wirth edward yourdon related fields computer science computer engineering project 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systems design approaches activitycentered adaptive web affective brainstorming by committee by contract ck theory closure codesign conceptoriented configuration contextual continuous cradletocradle creative problemsolving creativity techniques critical design fiction defensive designbidbuild designbuild architectled domaindriven ecodesign energy neutral engineering design process probabilistic design errortolerant faulttolerant frameworkoriented for assembly for behaviour change for manufacturability for six sigma for testing for x functional generative geodesign highlevel integrated integrated topside intelligencebased iterative kiss principle lowlevel metadesign mind mapping modular new wave objectoriented open parametric participatory platformbased policybased processcentered public interest rational regenerative reliability engineering researchbased responsibilitydriven rwd safelife sustainable systemic sod tableless web theory of constraints topdown and bottomup transformation 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chicago good design award japan graphex if product design award james dyson award prince philip designers prize related topics aesthetics agile concept art creative industries cultural icon design enterprise architecture futures studies innovation management intelligent design lean startup new product development ooda loop philosophy of design process simulation slow design steam fields unintelligent design visualization wicked problem design brief change classic director education elements and principles engineer firm history knowledge language life load museum paradigm rationale review specification studio technology commons wikibooks wikinews wikiquote wikisource wiktionary 