Title of Paper: OGC Services Catalog Prototype

Principal Author : Yonsook Enloe

Abstract: In open distributed archtectures for geographic systems such as that found in the OpenGIS Consortium (OGC) framework, there is a need for users to quickly and reliably discover, locate and identify desired data, associated services and supporting metadata. Catalog services provide the infrastructure to meet these needs. The major objectives of Catalog Services in such an environment are:

• Provide an OGC compliant interface for clients to find services of interest as well as for Service Providers to advertise their holdings.
• Support interoperability between other OGC Catalog Service compliant systems through the use of standardized metadata models and other well defined access interfaces.
• Support search distribution among OGC compliant Catalog systems, enabling clients to view collections of geographically separated and independently managed catalogs as single logical entities.

In the context of the OGC, a Web Service is defined to to be a collection of operations, accesible through the Web via. well defined interfaces for access to georeferenced information. Three principal types of services have been defined by OGC Web Mapping Testbed phase 2 activity: Web Map Service (WMS), Web Coverage Service (WCS) and Web Feature Service (WFS). In addition, the Geospatial Fusion Services (GFS) testbed defined services that return spatially referenced results: GeoParser, GeoCoder and GeoLinker. Collectively, these services are referred to as OGC Web Services.

A Services Catalog is a repository of metadata about these Web Services and supports registration, metadata harvesting and descriptor ingest, push and pull update of descriptors and discovery of service types and instances. it is a “stateless” catalog in that it relies on single request/response messages of HTTP on which it is based.

This presentation provides an overview of the design and implementation of a prototype OGC Services Catalog. Facilities are provided for the URL entry of OGC Web Service capabilities into the system for ingestion as well as the automatic harvesting of this data at prespecified intervals into the system to have it available for service discovery via. “viewer” clients. Service Providers may also view, modify and delete their entries from the system – modification and deletion operations require preconfigured privileges. In addition, service discovery is facilitated through a well defined search interface. Results of prototyping these interfaces, which specifies query language, namespaces, XML return formats etc. are also described.