The OGC and the World Wide Web Consortium Step Up Collaboration

Welcome to GISWeekly! This week our Industry News features a story on the OGC and the World Wide Web Consortium and their efforts to step up collaboration by Carl Reed.

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Industry News
The OGC and the World Wide Web Consortium Step Up Collaboration
by Carl Reed
Chief Technology Officer
Open Geospatial Consortium, Inc
tel: +1-970-419-8755

In 2003, the World Wide Web Consortium ( W3C) Semantic Web Interest Group published the “ Basic Geo Vocabulary”. The W3C is the standards organization that has developed and promoted essential Web standards such as HTML, XML, and others. “Basic Geo” is a specification that provides a “namespace” for representing latitude, longitude and elevation, using WGS84 as a reference datum.

This Geo note is not currently a W3C recommendation, and has not been subject to the associated review process, but it is being used in a variety of Web applications.

Many web developers were content with using Basic Geo in their applications. However, over time, Web developers discovered that they often require more capabilities than just expressing points. There is also the need to express, lines, polygons and coordinate reference systems. As GIS professionals can easily imagine, even basic location-based applications might require concepts like “route,” “is near,” “touches,” and “intersects,” and these capabilities are not supported in the Basic Geo vocabulary.

Fortunately, the OGC has, since 1994, engaged users and providers of geospatial technology in a standards process that has produced a wide range of geospatial standards. These include very simple “lightweight” profiles of the comprehensive XML-based OpenGISÆ Geography Markup Language (GML) Specification. These profiles provide needed guidance and information models required to update Basic Geo. Indeed, most of the geospatial standards developed and adopted by the OGC membership since 1998 have been built on Web standards from the W3C, OASIS and other organizations. Most of these are in the suite of standards that the OGC calls “OGC Web Services.”

The W3C is currently focused on an effort to specify ways of encoding natural language that enable much “smarter” searches. Their goal is the “Semantic Web.” Last year, the Open Geospatial ConsortiumÆ (OGC) became a member of the W3C and initiated a W3C incubator called Geospatial XG to focus attention on semantic geospatial issues.

Within the W3C, Incubator Activities like the Geospatial XG facilitate rapid development, on a time scale of a year or less, of new Web-related concepts. W3C members OGC, SRI International, University of Southern California Information Sciences Institute (USC ISI), Stanford University, and Oracle are sponsors of the Geospatial XG. Joshua Lieberman (Traverse Technology) chairs the group (Josh has also been active in the OGC since 1999). The expectation is that the work of the Geospatial XG will lead to collaborative “Geospatial Semantic Web” specification development involving the W3C and the OGC.

As GIS professionals know, metadata, vocabularies, and data model standards have long been an important focus of research and development in the geospatial world. GML, the OpenGISÆ Catalog Services Specification and other OGC standards leverage this distributed body of published knowledge and industry expertise and provides for capturing and expressing a basic level of geo-semantic context.

The first technical goal of the Geospatial XG is to address GeoRSS, a useful specification that was defined and released last year through an independent grassroots effort to provide the ability to encode “place” in RSS (“real simple syndication”) feeds. One serialization of GeoRSS already uses GML. (See sidebar.) The goal of the Geospatial XG activity is to make GeoRSS also work in an optimal way with the W3C’s Web Ontology Language (OWL)  .

Figure shows RSS “geospatially enabled” with GeoRSS. GeoRSS places no constraint on the type of syndication format. That is, it is not limited to RSS, but can be applied to other types of tags. (For the UML model of GeoRSS, see  )

GeoRSS is a significant enhancement beyond the W3C’s 2003 Basic Geo Vocabulary. Basic Geo provided only a fairly coarse spatial indexing capability, whereas the GeoRSS update supports a fuller sense of geographic representation, letting people add a feature "view" to any Web-accessible resource.

One might say that Basic Geo and GeoRSS are in a way the converse of traditional “GIS centricity”. They both support addition of feature properties to information, while traditional geo-centric models focus on adding information (properties) to features.

GML Profiles

1. The GML Point Profile is just five pages long. It is too limited to encode polygons or routing instructions, but many location-based services (LBS) applications work with just a coordinate pair that identifies the location of a device. Such devices are typically small and are expected to receive and send data quickly, so the data needs to be as compact as possible. The GML Point Profile is currently an OGC Discussion Paper.

2. The specification for a proposed GML Profile for GeoRSS fills fewer than 10 pages. RSS (Really Simple Syndication or Rich Site Summary) is a tool that enables Web users to subscribe to information updates from Web servers. The GML profile for GeoRSS ( GeoRSS) defines a GML-based structure to store spatial information in RSS web feeds. GeoRSS GML includes just four geometry types: point, line, polygon and box. GeoRSS was developed via consensus of a number of interested geospatial and IT professionals and is not currently an approved OGC specification.

3. The OpenGIS Æ GML Simple Feature Profile (GML SF) Specification, approved in 2006, is 31 pages in length (plus boilerplate and annexes). Its rules allow encoding of only simple feature geometries: points, lines, polygons and a few other geometry types. This subset is particularly useful for applications that intend to use the OpenGIS Web Feature Service Implementation Specification to define an interface for sharing and editing vector data.

4. GML in JPEG 2000 for Geographic Imagery Encoding Specification provides information related to an image, including image location. ISO, under whose auspices the JPEG 2000 Specification was developed, left a "box" available for storing such information. Encoding information about an image in GML provides a standard way for applications to find and use the image.

In terms of consortium process, the first goal of the Geospatial XG is to develop a W3C "Note" based on GeoRSS version 1. This will result in a W3C Web page describing GeoRSS in the context of both W3C standards, such as XML, HTML, and OWL, and OGC's relevant work, such as GML and the OpenGIS Abstract Specification.

The longer-term goal of the Geospatial XG is to improve collaboration between the W3C and the OGC with the objective that geospatial capabilities will ultimately be an integral, transparent and fully optimized component of the Web. The complexity and importance of geospatial technology are often not appreciated and are not easily understood without mutual consideration. Ultimately, the OGC and the W3C expect to collaboratively add geospatial content and context to the emerging Semantic Web in a manner that is consistent with existing and future OGC and W3C standards.

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Review Article
  • October 09, 2008
    Reviewed by 'Editor!!!'
    "The Brooks Act litigation and other issues affecting Federal procurement of surveying and mapping services will be the subject of a special presentation by John Palatiello at the ACSM Convention on Monday, March 12, in St. Louis. "
    LAST WEEK!!!!

      Was this review helpful to you?   (Report this review as inappropriate)

  • October 09, 2008
    Reviewed by 'Vikram'
    Atlast GML is getting due recognition ! It seems new, Web 2.0 applications will benefit from more concrete representation with GML schma.

      Was this review helpful to you?   (Report this review as inappropriate)

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