GIS Tech News #89 Aug, 2005 By: Arnie Williams
Focus on OGC
Open Geospatial Consortium shines as example
of interoperability excellence
In the past three issues of GIS Tech News (click here for archives),
we looked at case studies from the three primary PC-based GIS vendors —
Autodesk, ESRI and Intergraph. In this issue, we want to take a 30,000-foot view of GIS
related to open data architecture and interoperability issues. More than any other PC-based
discipline, GIS has led the way toward more open data exchange, and this primarily through one
organization, OGC (Open Geospatial Consortium). We'll take a brief look at the
organization's history and then focus on a few of OGC's current initiatives.
When the personal computer burst onto the scene in the early 1980s, it set the stage for a technology boom destined to change the world. Every aspect of life today seems to have some link to computing, and we've made much progress toward programming standards, but interoperability among diverse computer systems remains a highly charged issue today at computer conferences that address all aspects of technology, especially design.
GIS, too, has a history of competing proprietary systems that have clogged the pipeline for data sharing. But more than any other field, GIS has also taken steps to break through the quagmire. However, the discipline got off to a pretty rocky start.
In the mid-1980s, according to a report on the OGC Web site, GIS software was most heavily used in civil and government organizations — groups such as highways and transportation and the defense sector. These groups developed some very sophisticated GIS applications, but those were generally proprietary, internal programs that couldn't be shared for security reasons as well as program incompatibility.
The U.S. Fish and Wildlife Service was among the first to try to standardize software around a more open-architecture system with its MOSS (Map Overlay and Statistical System) software. MOSS was used by a number of U.S. Department of Interior agencies and state and local governments. The U.S. Corps of Army Engineers, through its CERL (Construction Engineering Research Laboratory), moved to an open UNIX environment and Internet system with its GRASS (Geographic Analysis Support System).
GRASS was actually a significant move in the right direction for open architecture, and it may have been the trend-setter without equal, except that for various reasons, it was moved out of government and into the private sector. Once private, it focused on three areas that were not primarily open-data oriented. Private GRASS aimed to make more geoprocessing choices available in the marketplace, act as a sounding board for the user community to make its wishes known to the development community and speed up procurement by aligning user needs with vendor product roadmaps.
Though free, modular and conducive to faster development, the GRASS initiative did not lead to greater interoperability among systems. The OpenGIS project, which led to the launch of the formal OGC in 1994, took interoperability as its primary focus, and its successes have set the standard for every other industry.
Between 1994 and 2004, OGC has grown from 20 members to more than 250 government, academic and private-sector organizations around the world. Among its members, you'll find almost all the technology vendors, along with technology integrators, data providers and location-based services companies.
From its inception OGC has sought a consensus process to define and agree to OpenGIS Abstract Specifications. These agreements help ensure that GIS programs enjoy the fullest interoperability achievable through developer cooperation.
OGC uses a three-program approach to reach open standards. First, specification program teams
composed of technical and planning committees work through a consensus process to define
specifications. Next, an interoperability program team guides a series of initiatives to
accelerate the development and acceptance of OpenGIS Specifications. And finally, a group
focused on outreach and community adoption offers resources to help technology developers take
advantage of OGC's open standards.
An example of a recent initiative is the GML Simple Features Specification Profile. GML (Geography Markup Language) is an XML grammar for encoding geographic information, including geographic features, coverage, observations, topology, geometry, coordinate reference systems, units of measure, time and value objects.
OGC put out a call to its members for input on developing the specification and received drafts from ESRI (United States), Cadcorp (United Kingdom), Galdos (Canada), Interactive Instruments (Germany), CSIRO (Australia), the U.S. Census Bureau and others.
Earlier this year OGC announced a Web Processing Services Interoperability experiment. The specification will be used to implement any kind of geospatial calculation or model as a Web service, so it can easily be found and invoked by a client.
A Worthy Model
OGC presents a working model worthy of emulation by other technology industries. Its members agree to share their intellectual property toward the development of specifications and standards that give geo data its widest possible dissemination and usability — an interoperability holy grail that seems more and more attainable, if OGC's 11-year history is any indication.
As design disciplines become even more global in this new century, proprietary data practices will make less sense. When developers finally wake up to this reality, they will have GIS and OGC to look to as models.
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