Transforming a Flat Metadata Schema to a Semantic Web Ontology: The Polish Digital Libraries Federation and CIDOC CRM Case Study

This paper describes the transformation of the metadata schema used by the Polish Digital Libraries Federation to the CIDOC CRM model implemented in OWL as Erlangen CRM. The need to transform the data from a flat schema to a full-fledged ontology arose during preliminary works in the Polish research project SYNAT. The Digital Libraries Federation site offers aggregated metadata of more than 600,000 publications that constitute the first portion of data introduced into the Integrated Knowledge System - one of the services developed in the SYNAT project. To be able to perform the desired functions, IKS needs heavily linked data that can be searched semantically. The issue is not only one of mapping one schema element to another, as the conceptualization of CIDOC is significantly different from that of the DLF schema. In the paper we identify a number of problems that are common to all such transformations and propose solutions. Finally, we present statistics concerning the mapping process and the resulting knowledge base.