Software design

From Wikipedia, the free encyclopedia

Software development process
Activities and steps
Requirements · Architecture
Design · Implementation
Testing · Deployment
Models
Agile · Cleanroom · Iterative · RAD
RUP · Spiral · Waterfall · XP · Scrum
Supporting disciplines
Configuration management
Documentation
Quality assurance (SQA)
Project management
User experience design
This box: view  talk  edit

Software design is a process of problem-solving and planning for a software solution. After the purpose and specifications of software is determined, software developers will design or employ designers to develop a plan for a solution. It includes low-level component and algorithm implementation issues as well as the architectural view.

The software requirements analysis (SRA) step of a software development process yields specifications that are used in software engineering. If the software is "semiautomated" or user centered, software design may involve user experience design yielding a story board 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.

A software design may be platform-independent or platform-specific, depending on the availability of the technology called for by the design.

Contents

[edit] Design Considerations

There are many aspects to consider in the design of a piece of software. The importance of each should reflect the goals the software is trying to achieve. Some of these aspects are:

  • Extensibility - New capabilities can be added to the software without major changes to the underlying architecture.
  • Robustness - The software is able to operate under stress or tolerate unpredictable or invalid input. For example, it can be designed with a resilience to low memory conditions.
  • Reliability - The software is able to perform a required function under stated conditions for a specified period of time.
  • Fault-tolerance - The software is resistant to and able to recover from component failure.
  • Security - The software is able to withstand hostile acts and influences.
  • Maintainability - The software can be restored to a specified condition within a specified period of time. For example, antivirus software may include the ability to periodically receive virus definition updates in order to maintain the software's effectiveness.
  • 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 backward-compatible with an older version of itself.
  • Modularity - the resulting software comprises well defined, independent components. That 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.
  • Reusability - the modular components designed should capture the essence of the functionality expected out of them and no more or less. This single-minded purpose renders the components reusable wherever there are similar needs in other designs.

[edit] Design Patterns

A software designer or architect may identify a design problem which has been solved by others before. A template or pattern describing a solution to a common problem is known as a design pattern. The reuse of such patterns can speed up the software development process, having been tested and proved in the past.

[edit] Design methodologies

Design methodologies aim to provide a template process or a framework for the actual design of a system. They aim to simplify the actual process of designing a system and aim to enforce some standard design principles which improve the quality of a design. One of the earlier design methodologies is the Responsibility Driven Design (RDD) pioneered by Rebecca Wirth et al. It forms the basis of the URDAD, the Use Case, Responsibility-Driven Analysis and Design method which aims to generate a technology neutral design which is then mapped onto one's choice of implementation architecture and technologies.

[edit] Usage

Software design documentation may be reviewed or presented to allow constraints, specifications and even requirements to be adjusted prior to 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 a professional approach. 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.

[edit] See also