Composing Mappings Between Schemas Using a Reference Ontology

Large-scale database integration requires a significant cost in developing a global schema and finding mappings between the global and local schemas. Developing the global schema requires matching and merging the concepts in the data sources and is a bottleneck in the process. In this paper we propose a strategy for computing the mapping between schemas by performing a composition of the mappings between individual schemas and a reference ontology. Our premise is that many organizations have standard ontologies that, although they may not be suitable as a global schema, are useful in providing standard terminology and naming conventions for concepts and relationships. It is valuable to leverage these existing ontological resources to help automate the construction of a global schema and mappings between schemas. Our system semi-automates the matching between local schemas and a reference ontology then automatically composes the matchings to build mappings between schemas. Using these mappings, we use model management techniques to compute a global schema. A major advantage of this approach is that human intervention in validating matchings mostly occurs during the matching between schema and ontology. A problem is that matching schemas to ontologies is challenging because the ontology may only contain a subset of the concepts in the schema or may be more general than the schema. Further, the more complicated ontological graph structure limits the effectiveness of some matchers. Our contribution is showing how schema-to-ontology matchings can be used to compose mappings between schemas with high accuracy by adapting the COMA schema matching system to work with ontologies.