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"Specification" redirects here. For other uses, see Specification (disambiguation).

Specification (often abbreviated as spec) may refer to an explicit set of requirements to be satisfied by a material, design, product, or service.[1] Should a material, product, or service fail to meet one or more of the applicable specifications, it may be referred to as being out of specification;[2] the abbreviation OOS may also be used.[3] In casual usage, underspec or overspec are used when something is worse or better than specified (compare overengineering), though in general (such as for sizes) there is only a notion of "in spec" or "out of spec", not "better" or "worse". A specification is a type of technical standard.

A technical specification may be developed by any of various kinds of organizations, both Telcordia Technologies). It is common for one organization to refer to (reference, call out, cite) the standards of another. Voluntary standards may become mandatory if adopted by a government or business contract.

A Design or Product Specification describes the features of the solutions for the Requirement Specification. Sometimes the term specification is here used in connection with a data sheet (or spec sheet). This may be confusing. A data sheet describes the technical characteristics of an item or product as designed and/or produced. It can be published by a manufacturer to help people choose products or to help use the products. A data sheet is not a technical specification as described in this article.


In engineering, manufacturing, and business, it is vital for suppliers, purchasers, and users of materials, products, or services to understand and agree upon all requirements.[4] A specification is a type of a standard which is often referenced by a contract or procurement document. It provides the necessary details about the specific requirements.

Specifications may be written by government agencies, standards organizations (ASTM, ISO, CEN, DoD, etc.), trade associations, corporations, and others.

A product specification does not necessarily prove a product to be correct or useful. An item might be verified to comply with a specification or stamped with a specification number: This does not, by itself, indicate that the item is fit for any particular use. The people who use the item (engineers, trade unions, etc.) or specify the item (building codes, government, industry, etc.) have the responsibility to consider the choice of available specifications, specify the correct one, enforce compliance, and use the item correctly. Validation of suitability is necessary.

Guidance and content

Sometimes a guide or a standing operating procedure is available to help write and format a good specification.[5][6][7][8] A specification might include:

Process capability considerations

A good engineering specification, by itself, does not necessarily imply that all products sold to that specification actually meet the listed targets and tolerances. Actual production of any material, product, or service involves inherent variation of output. With a normal distribution, the tails of production may extend well beyond plus and minus three standard deviations from the process average.

The process capability of materials and products needs to be compatible with the specified engineering tolerances. Process controls must be in place and an effective Quality management system, such as Total Quality Management, needs to keep actual production within the desired tolerances.

Effective enforcement of a specification is necessary for it to be useful.

Construction specifications in North America

Specifications in North America form part of the contract documents that accompany and govern the construction of a building. The guiding master document is the latest edition of MasterFormat. It is a consensus document that is jointly sponsored by two professional organisations: Construction Specifications Canada and Construction Specifications Institute.

While there is a tendency to believe that "Specs overrule Drawings" in the event of discrepancies between the text document and the drawings, the actual intent—made explicit in the contract between the Owner and the Contractor—is for the drawings and specifications to be complementary, together providing the information required for a complete facility.

The Specifications fall into 50 Divisions, or broad categories of work results involved in construction. The Divisions are subdivided into Sections, each one addressing a narrow scope of the construction work. For instance, firestopping is addressed in Section 078400 - Firestopping. It forms part of Division 07, which is Thermal and Moisture Protection. Division 07 also addresses building envelope and fireproofing work.

Each Section is subdivided into three distinct Parts: "General", "Products" and "Execution". The MasterFormat system can be successfully applied to residential, commercial, civil, and industrial construction.

Specifications can be either "performance-based", whereby the specifier restricts the text to stating the performance that must be achieved by the completed work, or "prescriptive", whereby the specifier indicates specific products, vendors and even contractors that are acceptable for each workscope. Most construction specifications are a combination of performance-based and prescriptive types, naming acceptable manufacturers and products while also specifying certain standards and design criteria that must be met.

While North American specifications are usually restricted to broad descriptions of the work, European ones can include actual work quantities, including such things as area of drywall to be built in square metres, like a bill of materials. This type of specification is a collaborative effort between a specwriter and a quantity surveyor. This approach is unusual in North America, where each bidder performs a quantity survey on the basis of both drawings and specifications.

Although specifications are usually issued by the architect's office, specwriting itself is undertaken by the architect and the various engineers or by specialist specwriters. Specwriting is often a distinct professional trade, with professional certifications such as "Certified Construction Specifier" (CCS) through the professional organizations noted above. Specwriters are either employees of or sub-contractors to architects, engineers, or construction management companies. Specwriters frequently meet with manufacturers of building materials who seek to have their products specified on upcoming construction projects so that contractors can include their products in the estimates leading to their proposals.

Construction specifications in the UK

Specifications in the UK are part of the contract documents that accompany and govern the construction of a building. They are prepared by construction professionals such as Architects, Architectural technologists, Structural Engineers, Landscape Architects and Building Services Engineers. They are created from previous project specifications, in-house documents or master specifications such as the National Building Specification (NBS). The National Building Specification is owned by the Royal Institute of British Architects (RIBA) through their commercial group RIBA Enterprises (RIBAe). NBS master specifications provide content that is broad and comprehensive, and delivered using software functionality that enables specifiers to customize the content to suit the needs of the project and to keep up to date. UK project specification types fall into two main categories prescriptive and performance. Prescriptive specifications define the requirements using generic or proprietary descriptions of what is required, whereas performance specifications focus on the outcomes rather than the characteristics of the components. Specifications are an integral part of Building Information Modeling and cover the non-geometric requirements.

Food and drug specifications

Pharmaceutical products can usually be tested and qualified by various Pharmacopoeia. Current existing pronounced standards include:

If any pharmaceutical product is not covered by the above standards, it can be evaluated by the additional source of Pharmacopoeia from other nations, from industrial specifications, or from a standardized formulary such as

A similar approach is adopted by the food manufacturing, of which Codex Alimentarius ranks the highest standards, followed by regional and national standards.[16]

The coverage of food and drug standards by ISO is currently less fruitful and not yet put forward as an urgent agenda due to the tight restrictions of regional or national constitution[17][18]

Specifications and other standards can be externally imposed as discussed above, but also intenal manufacturing and quality specifications. These exist not only for the food or pharmaceutical product but also for the processing machinery, quality processes, packaging, logistics (cold chain), etc. and are exemplified by ISO 14134 and ISO 15609[19][20]

The converse of explicit statement of specifications is a process for dealing with observations that are out-of-specification. The United States Food and Drug Administration has published a non-binding recommendation that addresses just this point.[3]

At the present time, much of the information and regulations concerning food and food products remain in a form which makes it difficult to apply automated information processing, storage and transmission methods and techniques.

Data systems that can process, store and transfer information about food and food products need formal specifications for the representations of data about food and food products in order to operate effectively and efficiently.

Development of formal specifications for food and drug data with the necessary and sufficient clarity and precision for use specifically by digital computing systems have begun to emerge from government agencies and standards organizations.

The United States Food and Drug Administration has published specifications for a "Structured Product Label" which drug manufacturers must by mandate use to submit electronically the information on a drug label.[21]

Recently, ISO has made some progress in the area of food and drug standards and formal specifications for data about regulated substances through the publication of ISO 11238[22]

Information technology

Specification need

Specifications are needed to avoid errors due to lack of specification, for instance, in interoperability issues.

For instance, when two applications share Unicode data, but use different normal forms or use them incorrectly, in an incompatible way or without sharing a minimum set of interoperability specification, errors and data loss can result. For example, Mac OS X has many components that prefer or require only decomposed characters (thus decomposed-only Unicode encoded with UTF-8 is also known as "UTF8-MAC"). In one specific instance, the combination of OS X errors handling composed characters, and the samba file- and printer-sharing software (which replaces decomposed letters with composed ones when copying file names), has led to confusing and data-destroying interoperability problems.[23][24]

Applications may avoid such errors by preserving input code points, and only normalizing them to the application's preferred normal form for internal use.

Such errors may also be avoided by with algorithms normalizing both strings before any binary comparison.

However errors due to filename encoding incompatibilities have always existed, due to a lack of minimum set of common specification between software hoped to be interoperable between various filesystem drivers, operatings systems, network protocols, and thousands of software packages.

Formal specification

Main article: Formal specification

A formal specification is a mathematical description of software or hardware that may be used to develop an implementation. It describes what the system should do, not (necessarily) how the system should do it. Given such a specification, it is possible to use formal verification techniques to demonstrate that a candidate system design is correct with respect to that specification. This has the advantage that incorrect candidate system designs can be revised before a major investment has been made in actually implementing the design. An alternative approach is to use provably correct refinement steps to transform a specification into a design, and ultimately into an actual implementation, that is correct by construction.

Program specification

A program specification is the definition of what a computer program is expected to do. It can be informal, in which case it can be considered as a user manual from a developer point of view, or formal, in which case it has a definite meaning defined in mathematical or programmatic terms. In practice, many successful specifications are written to understand and fine-tune applications that were already well-developed, although safety-critical software systems are often carefully specified prior to application development. Specifications are most important for external interfaces that must remain stable.

Functional specification

In software development, a functional specification (also, functional spec or specs or functional specifications document (FSD)) is the set of documentation that describes the behavior of a computer program or larger software system. The documentation typically describes various inputs that can be provided to the software system and how the system responds to those inputs.

Web service specification

Web services specifications are often under the umbrella of a quality management system.[25]

Document specification

These types of documents define how a specific document should be written, which may include, but is not limited to, the systems of a document naming, version, layout, referencing, structuring, appearance, language, copyright, hierarchy or format, etc.[26][27] Very often, this kind of specifications is complemented by a designated template.[28][29][30]

See also

Notes and references

Further reading

  • Pyzdek, T, "Quality Engineering Handbook", 2003, ISBN 0-8247-4614-7
  • Godfrey, A. B., "Juran's Quality Handbook", 1999, ISBN 007034003
  • "Specifications for the Chemical And Process Industries", 1996, ASQ Quality Press, ISBN 0-87389-351-4
  • ASTM E29-06b Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
  • Journal of Chemical Information and Modeling
  • Emerald Group Publishing, ISSN: 0022-0418

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