Metadata Exchange Research Articles

SEMEDA: ontology based semantic integration of biological databases

Many molecular biological databases are implemented on relational Database Management Systems, which provide standard interfaces like JDBC and ODBC for data and metadata exchange. By using these interfaces, many technical problems of database integration vanish and issues related to semantics remain, e.g. the use of different terms for the same things, different names for equivalent database attributes and missing links between relevant entries in different databases. In this publication, principles and methods that were used to implement SEMEDA (Semantic Meta Database) are described. Database owners can use SEMEDA to provide semantically integrated access to their databases as well as to collaboratively edit and maintain ontologies and controlled vocabularies. Biologists can use SEMEDA to query the integrated databases in real time without having to know the structure or any technical details of the underlying databases. SEMEDA is available at http://www-bm.ipk-gatersleben.de/semeda/. Database providers who intend to grant access to their databases via SEMEDA are encouraged to contact the authors.

Leveraging OAI harvesting to disseminate theses

NDLTD, the Networked Digital Library of Theses and Dissertations, supports and encourages the production and archiving of electronic theses and dissertations (ETDs). While many current NDLTD member institutions and consortia have individual collections accessible online, there has until recently been no single mechanism to aggregate all ETDs to provide NDLTD‐wide services (e.g. searching). With the emergence of the Open Archives Initiative (OAI), that has changed. The OAI’s Protocol for Metadata Harvesting is a robust interoperability solution that defines a standard method of exchanging metadata. While working with the OAI to develop and test the metadata harvesting standard, we have set up and actively maintain a central NDLTD metadata collection and multiple user portals. We discuss in this article our experiences in building this distributed digital library based upon the work of the OAI.

A case study in metadata harvesting: the NSDL

This paper describes the use of the Open Archives Initiative Protocol for Metadata Harvesting in the NSF’s National Science Digital Library (NSDL). The protocol is used both as a method to ingest metadata into a central Metadata Repository and also as the means by which the repository exports metadata to service providers. The NSDL Search Service is used to illustrate this architecture. An early version of the Metadata Repository was an alpha test site for version 1 of the protocol and the production repository was a beta test site for version 2. This paper describes the implementation experience and early practical tests. Despite some teething troubles and the long‐term difficulties of semantic compatibility, the overall conclusion is optimism that the Open Archive Initiative will be a successful part of the NSDL.

Querying the Semantic Web with RQL

Real-scale Semantic Web applications, such as Knowledge Portals and E-Marketplaces, require the management of voluminous repositories of resource metadata. The Resource Description Framework (RDF) enables the creation and exchange of metadata as any other Web data. Although large volumes of RDF descriptions are already appearing, sufficiently expressive declarative query languages for RDF are still missing. We propose RQL, a new query language adapting the functionality of semistructured or XML query languages to the peculiarities of RDF but also extending this functionality in order to uniformly query both RDF descriptions and schemas. RQL is a typed language, following a functional approach a la OQL and relies on a formal graph model that permits the interpretation of superimposed resource descriptions created using one or more RDF schemas. We illustrate the syntax, semantics and type system of RQL and report on the performance of RSSDB, our persistent RDF Store, for storing and querying voluminous RDF metadata.

Metadata: A Fundamental Component of the Semantic Web

Metadata: A Fundamental Component of the Semantic Web