FAQs - OGC Abstract Spec

Q and A: 
  1. What is the "Abstract Specification" and what are "implementation specifications"?
  2. What's the difference between a specification and a standard?
  3. What is the "OGC Technical Baseline"?
  4. What is the OpenGIS Reference Model (ORM)?
  5. What OpenGIS Implementation Specifications have been completed?
  6. What OpenGIS Specifications remain to be developed?
  7. What are OGC Web Services (OWS)?
  8. What other distributed computing platforms does OGC work on besides the Web?

A: The OpenGIS Abstract Specification formally documents, at a "high level," the terms, definitions and information models, such as geometry, along with software behaviors, on which members have reached consensus. Thus, the Abstract Specification provides the lingua franca and foundation upon which OpenGIS Implementation Specification are based. OpenGIS implementation specifications are actual engineering specifications that software developers can implement in applications and products. (For an example of the Abstract Specification, see Topic 2: Spatial Reference Systems. For an example of an implementation specification, see OpenGIS® Web Map Service Implementation Specification.)

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A: A standard is a specification, but a specification is not necessarily a standard. In the context of geoprocessing, specifications (whether they are standards or not) are documents that describe protocols (e.g., TCP/IP), data encodings (e.g., GML), software interfaces, and other aspects of information and process sharing. They provide guidance to the software developer regarding software design and behavior. A standard is a specification that developers in numerous companies can use to ensure that their products "work together." (In the context of geodata, specifications can describe content (e.g. ISO 19115 Metadata Content Standard), formats (e.g. JPEG, PNG), schemas, quality, etc.)

The authority of a specification rests on its inherent technical excellence. On the other hand, the authority of a standard derives from the breadth of its acceptance in the marketplace and the authority of the standard setting organization sponsoring it. The standard setting organization may be an industry standards consortium such as OGC, W3C or IETF or it may be an official standards organization such as the International Organization for Standardization (ISO) or ANSII. Both types of organizations develop specifications that are intended to be standards.

Every software company develops specifications to guide development of their proprietary technologies. Sometimes these are later released to the public, usually to strengthen the competitive market position of the vendor. Such proprietary specifications may become "de facto" standards.

OpenGIS® Specifications, on the other hand, are "consensus standards" similar to HTML, XML, TCP/IP and the other standards that define the Internet and the Web. OpenGIS Specifications are conceived, written, and approved through a member consensus process. This process includes active participation and review by users, integrators and vendors. Thus OpenGIS Specifications are technically of very high quality, they are specific enough to ensure interoperability, and they are standards by virtue of the market acceptance that results from the participation in OGC of so many of the industry's key technology providers and users. Several OpenGIS Specifications have also been adopted by ISO as International Standards and more are in ISO's review process.

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A: The OGC Technical Baseline is the set of all Adopted Specifications plus all other technical documents that have been approved by the OGC Technical and Planning Committees, including the OpenGIS Reference Model, OpenGIS Abstract Specifications, Recommendation Papers, and Discussion Papers.

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A: The ORM is a document, part of the OGC Technical Baseline, that provides an overall conceptual framework for building geospatial processing into distributed systems in an incremental and interoperable manner. The ORM serves as a guide to designing enterprise architectures whose data models and open interfaces support the near-term and long-term vendor-neutral integration of spatial capabilities.

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A: Click on "Documents =>OpenGIS Specifications" on OGC's web page or go directly to them to see the current list of adopted OpenGIS Implementation Specifications.

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A: Many OpenGIS Specifications are in process and others are sure to be proposed. You can learn about many of those that are in process by reviewing the Requests For Comment, Recommendation Papers, and Discussion Papers that can be accessed through the OGC Web site home page.

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A: OWS refers to all OpenGIS Specifications for interfaces, encodings, etc. that apply to Web-based geoprocessing. (Some OpenGIS Specifications apply in the case of two dissimilar systems communicating while running on the same computer or while using a distributed computing platform other than the Web.)

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A: OGC members have developed OpenGIS Specifications for CORBA and SQL. Work on "Geospatial Objects" will yield a set of specifications that are "distributed computing platform" neutral (like the OpenGIS Abstract Specifications) but that can be automatically generated for a specific distributed computing platform using UML tools.

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