FURPS+ Model

Requirements

Requirements are capabilities and conditions to which the system must conform. A prime challenge of requirements work is to find, communicate, and record what is really needed, in a form that clearly speaks to the client and development team members.

What are the types and categories of Requirements?

In UP requirements are categorized according to FURPS+ model. The FURPS is a technique to validate the prioritized requirements after an understanding with client’s needs and necessities. The acronym FURPS stands for Functionality, Usability, Reliability, Performance, and Supportability.

• Functionality – The F in the FURPS+ acronym represents the main product features that are familiar within the business domain of the solution being developed. Functional requirements may include:
• Features
• Capabilities
• Security
• Usability – Usability includes looking at, capturing, and stating requirements based around user interface issues.Usability requirements may include:
• Human factors
• Help and Documentation
• Interface aesthetics, and consistency within the user interface
• Reliability– Reliability includes aspects such as:
• Frequency of failure
• Availability
• Recoverability
• Predictability
For example, computations, or recoverability of the system from shut-down failure.
• Performance – Performance involves things such as:
• Throughputof information through the system
• System response time.
• Recovery time.
• Start-up time.
• Accuracy
• Availability
• Resource usage
• Supportability – specify number of other requirements such as:
• Testability
• Adaptability
• Maintainability
• Compatibility
• Configurability
• Installability
• Scalability
• Localizability, and so on.

The “+” of the FURPS+ indicates ancillary and sub-factors to specify constraints, including design, implementation, interface, and physical constraints.

• Design Constraints – A design constraint, as the name implies, limits the design — for example, requiring a relational database stipulates the approach that we take in developing the system.
• Implementation Constraints – An implementation constraint puts limits on coding or construction – standards, platform, or implementation language.
• Interface Constraints – An interface constraint is a requirement to interact with an external item. When you develop within an enterprise, quite often you have to interact with external systems
• Physical constraints – Physical constraints affect the hardware used to house the system – for example, shape, size, and weight.