Extending VoID for Expressing Connectivity Metrics of a Semantic Warehouse

VoID (Vocabulary of Interlinked Datasets) has been proposed by W3C as the vocabulary for expressing metadata about RDF datasets. Despite its important contributions, VoID cannot express metadata that concern the connectivity of semantic warehouses. We use the term semantic warehouse to refer to a read-only set of RDF triples fetched (and transformed) from different sources that aims at serving a particular set of query requirements. Connectivity metrics are important for evaluating the value of a semantic warehouse, since they reflect its query capabilities. Moreover they also quantify the contribution of each constituent source to the warehouse. To allow the representation, exchange, and querying of such measurements, in this paper we describe an extension of VoID that allows representing them. We demonstrate its applicability through the case of a real and operational semantic warehouse for the marine domain.