Principles of database and knowledge-base systems, Vol. I
Principles of database and knowledge-base systems, Vol. I
Logical foundations of object-oriented and frame-based languages
Journal of the ACM (JACM)
Knowledge representation: logical, philosophical and computational foundations
Knowledge representation: logical, philosophical and computational foundations
On the Semantics of Anonymous Identity and Reification
On the Move to Meaningful Internet Systems, 2002 - DOA/CoopIS/ODBASE 2002 Confederated International Conferences DOA, CoopIS and ODBASE 2002
Three Implementations of SquishQL, a Simple RDF Query Language
ISWC '02 Proceedings of the First International Semantic Web Conference on The Semantic Web
Foundations of semantic web databases
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Semantics and complexity of SPARQL
ACM Transactions on Database Systems (TODS)
Semantics and complexity of SPARQL
ISWC'06 Proceedings of the 5th international conference on The Semantic Web
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This paper introduces and develops an algebra over triadic relations (relations whose contents are only triples). In essence, the algebra is a severely restricted variation of relational algebra (RA) that is de.ned over relations with exactly three attributes and is closed for the same set of relations. In particular, arbitrary joins and Cartesian products are replaced by a single three-way join. Ternary relations are important because they provide the minimal, and thus most uniform, way to encode semantics wherein metadata may be treated uniformly with regular data; this fact has been recognized in the choice of triples to formalize the Semantic Web via RDF. Indeed, algebraic de.nitions corresponding to certain of these formalisms will be shown as examples. An important aspect of this algebra is an encoding of triples, implementing a kind of rei.cation. The algebra is shown to be equivalent, over non-rei.ed values, to a restriction of Datalog and hence to a fragment of .rst order logic. Furthermore, the algebra requires only two operators if certain .xed in.nitary constants (similar to Tarski's identity) are present. In this case, all structure is represented only in the data, that is, in the encodings that these in.nitary constants represent.