Software design

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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. [1] Software design may refer to either "all the activity involved in conceptualizing, framing, implementing, commissioning, and ultimately modifying complex systems" or "the activity following requirements specification and before programming, as ... [in] a stylized software engineering process." [2]

Agency is the capacity of an actor to act in a given environment. The capacity to act does not at first imply a specific moral dimension to the ability to make the choice to act, and moral agency is therefore a distinct concept. In sociology, an agent is an individual engaging with the social structure. Notably, though, the primacy of social structure vs. individual capacity with regard to persons' actions is debated within sociology. This debate concerns, at least partly, the level of reflexivity an agent may possess.

An artifact is one of many kinds of tangible by-products produced during the development of software. Some artifacts help describe the function, architecture, and design of software. Other artifacts are concerned with the process of development itself—such as project plans, business cases, and risk assessments.

Goal desired result or outcome

A goal is an idea of the future or desired result that a person or a group of people envisions, plans and commits to achieve. People endeavor to reach goals within a finite time by setting deadlines.

Contents

Software design usually involves problem solving and planning a software solution. This includes both a low-level component and algorithm design and a high-level, architecture design.

Software non-tangible executable component of a computer

Computer software, or simply software, is a collection of data or computer instructions that tell the computer how to work. This is in contrast to physical hardware, from which the system is built and actually performs the work. In computer science and software engineering, computer software is all information processed by computer systems, programs and data. Computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be realistically used on its own.

Software architecture refers to the high level structures of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations. The architecture of a software system is a metaphor, analogous to the architecture of a building. It functions as a blueprint for the system and the developing project, laying out the tasks necessary to be executed by the design teams.

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 "semi-automated" 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 semi-standard 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 platform-independent or platform-specific, depending upon the availability of the technology used for the design.

In software engineering, a software development process is the process of dividing software development work into distinct phases to improve design, product management, and project management. It is also known as a software 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.

Software engineering is the application of engineering to the development of software in a systematic method.

User experience design is the process of enhancing user satisfaction with a product by improving the usability, accessibility, and pleasure provided in the interaction with the product. User experience design encompasses traditional human–computer interaction (HCI) design, and extends it by addressing all aspects of a product or service as perceived by users.

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.

In computer programming, a software framework is an abstraction in which software providing generic functionality can be selectively changed by additional user-written code, thus providing application-specific software. A software framework provides a standard way to build and deploy applications. A software framework is a universal, reusable software environment that provides particular functionality as part of a larger software platform to facilitate development of software applications, products and solutions. Software frameworks may include support programs, compilers, code libraries, tool sets, and application programming interfaces (APIs) that bring together all the different components to enable development of a project or system.

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 architect’s plans for a house. It begins by representing the totality of the thing that is to be built (e.g., a three-dimensional rendering of the house); slowly, the thing is refined to provide guidance for constructing each detail (e.g., 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 [3] suggests a set of principles for software design, which have been adapted and extended in the following list:

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:

  1. 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 purpose. It is an act of Representing essential features without including the background details or explanations.
  2. Refinement - It is the process of elaboration. A hierarchy is developed by decomposing a macroscopic statement of function in a step-wise 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.
  3. Modularity - Software architecture is divided into components called modules.
  4. 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, e.g. in terms of performance, quality, schedule and cost.
  5. Control Hierarchy - A program structure that represents the organization of a program component and implies a hierarchy of control.
  6. 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.
  7. Data Structure - It is a representation of the logical relationship among individual elements of data.
  8. Software Procedure - It focuses on the processing of each module individually.
  9. 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. [4] The acronym PHAME (Principles of Hierarchy, Abstraction, Modularisation, and Encapsulation) is sometimes used to refer to these four fundamental principles. [5]

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:

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:

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. [8]

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, [9] and Donald Knuth used his experience writing TeX to describe the futility of attempting to design a program prior to implementing it:

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. [10]

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, [11] 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.

See also

Related Research Articles

In software engineering and computer science, abstraction is:

Data model abstract model for organizing data; abstract model that organizes elements of data and standardizes how they relate to one another and to properties of the real world entities

A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to properties of the real world entities. For instance, a data model may specify that the data element representing a car be composed of a number of other elements which, in turn, represent the color and size of the car and define its owner.

Model–view–controller

Model–View–Controller is an architectural pattern commonly used for developing user interfaces that divides an application into three interconnected parts. This is done to separate internal representations of information from the ways information is presented to and accepted from the user. The MVC design pattern decouples these major components allowing for efficient code reuse and parallel development.

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.

IDEF

IDEF, initially abbreviation of ICAM Definition, renamed in 1999 as Integration DEFinition, refers to a family of modeling languages in the field of systems and software engineering. They cover a wide range of uses, from functional modeling to data, simulation, object-oriented analysis/design and knowledge acquisition. These "definition languages" were developed under funding from U.S. Air Force and although still most commonly used by them, as well as other military and United States Department of Defense (DoD) agencies, are in the public domain.

Systems development life cycle

The systems development life cycle (SDLC), also referred to as the application development life-cycle, is a term used in systems engineering, information systems and software engineering to describe a process for planning, creating, testing, and deploying an information system. The systems development lifecycle concept applies to a range of hardware and software configurations, as a system can be composed of hardware only, software only, or a combination of both. There are usually six stages in this cycle: analysis, design, development and testing, implementation, documentation, and evaluation.

Software prototyping is the activity of creating prototypes of software applications, i.e., incomplete versions of the software program being developed. It is an activity that can occur in software development and is comparable to prototyping as known from other fields, such as mechanical engineering or manufacturing.

Object-oriented analysis and design (OOAD) is a popular technical approach for analyzing and designing an application, system, or business by applying object-oriented programming, as well as using visual modeling throughout the development life cycles to foster better stakeholder communication and product quality.

Domain engineering, also called product line engineering, is the entire process of reusing domain knowledge in the production of new software systems. It is a key concept in systematic software reuse. A key idea in systematic software reuse is the domain. Most organizations work in only a few domains. They repeatedly build similar systems within a given domain with variations to meet different customer needs. Rather than building each new system variant from scratch, significant savings may be achieved by reusing portions of previous systems in the domain to build new ones.

Presentation–abstraction–control

Presentation–abstraction–control (PAC) is a software architectural pattern. It is an interaction-oriented software architecture, and is somewhat similar to model–view–controller (MVC) in that it separates an interactive system into three types of components responsible for specific aspects of the application's functionality. The abstraction component retrieves and processes the data, the presentation component formats the visual and audio presentation of data, and the control component handles things such as the flow of control and communication between the other two components.

Object-oriented design is the process of planning a system of interacting objects for the purpose of solving a software problem. It is one approach to software design.

Dualistic Petri nets (dPNs) are a process-class variant of Petri nets. Like Petri nets in general and many related formalisms and notations, they are used to describe and analyze process architecture.

Enterprise modelling

Enterprise modelling is the abstract representation, description and definition of the structure, processes, information and resources of an identifiable business, government body, or other large organization.

Structured analysis method for analyzing and converting business requirements into specifications

In software engineering, structured analysis (SA) and structured design (SD) are methods for analyzing business requirements and developing specifications for converting practices into computer programs, hardware configurations, and related manual procedures.

Software analysis patterns or analysis patterns in software engineering are conceptual models, which capture an abstraction of a situation that can often be encountered in modelling. An analysis pattern can be represented as "a group of related, generic objects (meta-classes) with stereotypical attributes, behaviors, and expected interactions defined in a domain-neutral manner."

In computing, aspect-oriented software development (AOSD) is a software development technology that seeks new modularizations of software systems in order to isolate secondary or supporting functions from the main program's business logic. AOSD allows multiple concerns to be expressed separately and automatically unified into working systems.

IDEF4

IDEF4, or Integrated DEFinition for Object-Oriented Design, is an object-oriented design modeling language for the design of component-based client/server systems. It has been designed to support smooth transition from the application domain and requirements analysis models to the design and to actual source code generation. It specifies design objects with sufficient detail to enable source code generation.

References

  1. Ralph, P. and Wand, Y. (2009). A proposal for a formal definition of the design concept. In Lyytinen, K., Loucopoulos, P., Mylopoulos, J., and Robinson, W., editors, Design Requirements Workshop (LNBIP 14), pp. 103–136. Springer-Verlag, p. 109 doi : 10.1007/978-3-540-92966-6_6.
  2. Freeman, Peter; David Hart (2004). "A Science of design for software-intensive systems". Communications of the ACM. 47 (8): 19–21 [20]. doi:10.1145/1012037.1012054.
  3. Davis, A:"201 Principles of Software Development", McGraw Hill, 1995.
  4. Booch, Grady; et al. (2004). Object-Oriented Analysis and Design with Applications (3rd ed.). MA, USA: Addison Wesley. ISBN   0-201-89551-X . Retrieved 30 January 2015.
  5. Suryanarayana, Girish (November 2014). Refactoring for Software Design Smells. Morgan Kaufmann. p. 258. ISBN   978-0128013977 . Retrieved 31 January 2015.
  6. Carroll, John, ed. (1995). Scenario-Based Design: Envisioning Work and Technology in System Development. New York: John Wiley & Sons. ISBN   0471076597.
  7. Bell, Michael (2008). "Introduction to Service-Oriented Modeling". Service-Oriented Modeling: Service Analysis, Design, and Architecture. Wiley & Sons. ISBN   978-0-470-14111-3.
  8. Judith Bishop. "C# 3.0 Design Patterns: Use the Power of C# 3.0 to Solve Real-World Problems". C# Books from O'Reilly Media. Retrieved 2012-05-15. If you want to speed up the development of your .NET applications, you're ready for C# design patterns -- elegant, accepted and proven ways to tackle common programming problems.
  9. Dijkstra, E. W. (1988). "On the cruelty of really teaching computing science" . Retrieved 2014-01-10.
  10. Knuth, Donald E. (1989). "Notes on the Errors of TeX" (PDF).
  11. Ralph, P., and Wand, Y. A Proposal for a Formal Definition of the Design Concept. In, Lyytinen, K., Loucopoulos, P., Mylopoulos, J., and Robinson, W., (eds.), Design Requirements Engineering: A Ten-Year Perspective: Springer-Verlag, 2009, pp. 103-136

^ Roger S. Pressman. Software engineering: a practitioner’s approach. McGraw-Hill. ISBN   0-07-365578-3.