Specification

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A specification is an explicit set of requirements to be satisfied by a material, product, or service. (ASTM definition)

Use of a Specification 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. 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, International Organization for Standardization , CEN, etc), trade associations, corporations, and others.

A product specification does not necessarily prove the product to be correct. Just because an item is stamped with a specificaiton number 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 available specifications, specify the correct one, enforce compliance, and use the item correctly. Validation of suitability is necessary.

An example of a US Federal specification is FIPS-PUB 159, Detail Specification for 62.5-μm Core Diameter/125-μm Cladding Diameter Class Ia Multimode Optical Fibers. (Source: from Federal Standard 1037C and from MIL-STD-188)

Content of a Specification A specification might include:

Descriptive title and scope of the specification
Date of last effective revision and revision designation
Person, office, or agency responsible for questions on the specification, updates, and deviations.
The significance or importance of the specification and its intended use.
Terminology and definitions to clarify the meanings of the specification
Test methods for measuring all specified characteristics
Material requirements: physical, mechanical, electrical, chemical, etc. Targets and Tolerance (engineering).
Performance requirements. Targets and Tolerance (engineering).
Workmanship
Certifications required.
Safety considerations and requirements
Natural environment considerations and requirements
Quality requirements, Sampling (statistics), inspections, acceptance criteria
Person, office, or agency responsible enforcement of the specification.
Completion and delivery.
Provisions for rejection, reinspection, rehearing, corrective measures
etc

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 National MasterFormat. It is a consensus document that is jointly sponsored by two professional organisations:

Construction Specifications Canada
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 is for drawings and specifications to be complimentary with neither taking precedence over the other.

The Specifications fall into 50 "Divisions", or broad categories of work involved in construction. The "Divisions" are subdivided into "Sections", that address specific workscopes. For instance, firestopping is addressed in Section 078400 - Firestopping. It forms part of the Division 7, which is Thermal and Moisture Protection. Division 7 also addresses building envelope and fireproofing work. Each Section is subdivided into three distinct areas: "General", "Products" and "Execution". The National MasterFormat system has been uniformly applied to residential, commercial and much though not all industrial work.

Specifications can be another "performance-based", whereby the specifier restricts the text to stating the performance that must be achieved in each Section of work, or "prescriptive", whereby the specifier indicates specific products, vendors and even contractors that are acceptable for each workscope.

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 his or her own quantity survey on the basis of both drawings and specifications.

Specification writing is a professional trade with its own professional designations, such as "CCS", which means "Certified Construction Specifier". Specwriters can be either employees of or sub-contractors to architects. 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.

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 deviarions 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.

Software development Formal specification A formal specification is a mathematics 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 the 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 blueprint or user manual from a developer point of view, or Formal specification, in which case it has a definite meaning defined in mathematics or programmatic terms. In practice, most 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.

See also

Defense Standard
MasterFormat
Construction Specifications Institute
Requirements analysis
Submittals (construction)
Shop drawing
Statistical interference
Tolerance (engineering)
Performance testing
Verification
Verification and Validation‎

External links

Construction Specifications Library (US) by Arcat
Directory of US/Canadian Construction Products by 4specs

References

Pyzdek, T, "Quality Engineering Handbook", 2003, ISBN 0824746147
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

specification from FOLDOC
specification < jargon > (spec) A document describing how some system should work. (2001-02-06) Try this search on Wikipedia, OneLook, Google

functional specification from FOLDOC
functional specification < programming, project > A description of what a system (e.g. a piece of software) does or should do (but not how it should do it).

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