Software For Distributed Metadata Catalogue Services to Support The EU Portal


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The main goal of this study was to support the development of the prototype EU geoportal to access distributed metadata catalogues and search for metadata in a harmonized and interoperable way. This includes a number of software components, all of them off-the-shelf products, listed as follows:

• Catalogue service: a centralized broker (itself a catalogue service) that executes a query coming from a client, distributes the query to a known set of federated catalogue services, cumulates the results retuned and gives this response back to the client.
• Service monitor: a component to monitor the quality of services in an SDI
• Security manager: a component that handles security issues within an SDI
• Map client: a component to access standardized web map services and provide additional navigation and query tools to the user.

The main challenge is to set up the catalogue service as a broker to support distributed search against federated catalogues. Furthermore, the integration of catalogue broker and the remaining software components into the existing EU portal software is crucial. In addition to an appropriate federated search mechanism, a concept for the management of federated catalogue service is developed and implemented in the broker component.

The study is tightly aligned with the work of the INSPIRE drafting teams (DT) on metadata and networks services. The results of this study provide useful feedback in the development of the INSPIRE draft implementing rules. Thus, the study is meant to be a test case for two reasons both the rules defined by the INSPIRE DTs so far and the degree of interoperability of existing catalogue specifications.

The basic assumption is determined by the concept of distributed catalogue services defined by the OGC base specification CS 2.0. This concept provides a means to derive specific profiles of catalogue service specifications from the base specification whereas certain aspects have to be supported by the derived profiles (like query language, queryables, bindings, minimum Dublin core information model, etc.). Catalogue services based on a profile should then be able to interoperate on the level of that base specification.

Along with the base specification two existing profiles were considered: one based on ebRIM information model (a more general model coming defined by OASIS) and the ISO profile (a more specific model based on ISO 19115 and ISO 19119).

Many catalogues from different European member states contributed their catalogue implementations and knowledge to the study. In the end, two ISO based catalogue service implementations, two ebRIM and two OGC core catalogues (which implement the plain base specification) were integrated.

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