Interoperability Between Geoscience And Geospatial Catalog Protocols

In the past several years, interoperability gaps have made cross-protocol and cross-community data access a challenge within the Earth science community. One such gap is between two protocol families developed within the geospatial and Earth science communities. The Earth science community has developed a family of related geoscience protocols that includes OPeNDAP for data access and the Thematic Real-time Environmental Distributed Data Services (THREDDS) catalog capability. The corresponding protocols in the geospatial community are the Open Geospatial Consortium (OGC) protocols Web Coverage Service for geospatial data access and Catalog Services for Web (CSW) for data search. We have developed a catalog gateway to mediate client/server interactions between OGC catalog clients and THREDDS servers. In essence, the gateway is an OGC Catalog server that enables OGC clients to search for data registered in THREDDS catalogs. The gateway comprises two parts: the CSW server and a THREDDS-to-CSW ingestion tool. There are two key challenges in constructing such gateway, the first is to define the mapping relationship between the catalog metadata schema of CSW and that of the THREDDS, and the second one is to ingest the THREDDS catalog content into the CSW server. Since our CSW server is based on the ISO19115/ISO19119 Application Profile, a key challenge is to semantically map the ISO 19115 metadata attributes in ISO Application Profile to the THREDDS metadata attributes in the THREDDS Dataset Inventory Catalog Specification Version 1.0. With the mapping established, tools that translate the THREDDS catalog information model into the CSW/ISO Profile information model were developed. These dynamically poll THREDDS catalog servers and ingest the THREDDS catalog information into the CSW server's database, maintaining the hierarchical relationships inherent in the THREDDS catalogs. A prototype system has been implemented to demonstrate the concept and approach.