Construction of marine vocabularies in the Marine Metadata Interoperability Project

Data producers often overlook existing metadata descriptors and controlled vocabularies for describing their data, opting instead to create custom descriptors and vocabularies. One of the objectives of the Marine Metadata Interoperability (MMI) project is to reduce this vocabulary proliferation. The work is accomplished as community collaborations, which are supported via the content management framework of the MMI Web site. Services, processes, techniques, and advice are all offered via the community Web site supported by the MMI (http://marinemetadata.org). As part of the services, MMI has created and made available marine ontologies based on existing vocabularies. Ontologies are an explicit and formal specification of mental abstractions. Ontologies are being published using the Web Ontology Language (OWL), the ontology expression tool recommended by the World Wide Web Consortium (W3C), and made available using Web services. By providing these services using common terminology, the MMI effort facilitates discovery, sharing, and markup of marine data. The MMI methodology for creating the marine ontologies is composed of: identification, harmonization, alignment and mapping, and publication. First the marine vocabulary is identified. The namespace and the required transformation are then documented. Then the vocabulary is harmonized with the other vocabularies by transforming the vocabulary into a common structure, in this case OWL format. Having all the marine vocabularies harmonized in OWL allows alignment and mapping between the vocabularies. OWL allows the required mapping relationships such as "same As", "narrower Than", and "broader Than". Finally, the ontologies are published via Web services. The first three parts of this methodology, which form the foundation for the development of true semantic interoperability, will be discussed in this paper.