Home Articles Potential of Using Web Services in Distributed GIS Applications

Potential of Using Web Services in Distributed GIS Applications

Pouria Amirian
Faculty of Geodesy and
Geomatics Engineering, K. N. Toosi University of Technology
Vali-e-asr St., Mirdamad Cross, Tehran, Iran
[email protected]

Ali Mansurian
Faculty of Geodesy and
Geomatics Engineering, K. N. Toosi University of Technologyb
Vali-e-asr St., Mirdamad Cross, Tehran, Iran
[email protected]

Introduction
Nowadays, individuals, universities, organizations and companies use the Web as a main infrastructure to publish spatial information, offer or consume GIS services and in some rare cases to conduct a complicated GIS processing.

Due to the high potential of Internet and Web, many different Web mapping software packages have been provided by different GIS vendors. But each Web mapping software, utilize different technologies, which are not able to interact and interoperate with each other directly. For this reason, service on a particular GIS server can only be accessed by its own clients and other clients (clients of other GIS servers) cannot access services of that server.

On the other hand, application-integration is not supported with current Web mapping software. Today, GIS developers can’t combine specific services from different Web mapping software, and use them as building block of an integrated GIS application. These problems arise because of this fact that, Internet-based applications need to be able to interact with other Internet-based applications as easily as interactions between Web browsers and Web servers. But the essentially text-based Web does not support software interaction very well.

A more efficient method is needed to allow applications, interact directly with other applications to automatically and without human intervention, executing instructions that would otherwise have to be entered manually through Web browser (Cerami 2002). But the main barrier in front of application-to-application interactions is the interoperability. The following section will describe spatial interoperability and different aspects and resources of this problem.

Spatial Interoperability
The most important problem associated with GIS systems is non-Interoperability of these systems. Based on OGC’s reference model (OGC 2003) interoperability refers to “capability to communicate, execute programs, or transfer data among various functional units in a manner that requires the user to have little or no knowledge of the unique characteristics of those units”.

According to OGC 2004 and the mentioned definition, five sources for spatial non-interoperability could be identified:

  • Different types of geoprocessing systems (Vector, Raster, CAD, etc. ) produce very different types of data.
  • Different vendors’ geoprocessing systems use internal data formats and produce data in formats that are different and in most cases proprietary.
  • Different vendors’ systems use proprietary software access methods with proprietary interfaces that restrict opportunities for network inter-process communication between systems.
  • Different data producers, even if using the same type of system from the same vendor, do not, name spatial features in the same way.
  • Different data producers, if they provide metadata, do not, structure their metadata in standard schemas that enable effective metadata searches.

In this list the items one, two and three are the causes of technical non-interoperability and items number four and five are the causes of semantic non-interoperability. As GIS community believes, solution for semantic non-interoperability is consensus development of interoperable standards and specifications.

In this context, OGC plays a major role by setting the Industry standards for GIS services. Generally the main goal of OGC is to promote the widespread use of interoperable GIS services throughout the information infrastructure. In GIS community solutions for overcoming technical non-interoperability have changed with the development of new technologies in IT world. In IT world, the best solution for providing interoperability among heterogeneous systems in distributed, decentralized environments are Web services technologies (Volter et al 2005).

Following sections will briefly introduce the concepts of Web services and GIS Web service as well as how Web services can overcome the mentioned problem.

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