ORDI SG Tripleset Model

ORDI SG specifies a uniform structured data model that is defined as an extension of RDF, introducing Named Graphs and Triplesets. Named Graphs (NG) were introduced in [1], as a mechanism for referring to and describing RDF graphs. The name of each NG is an URI, which can be used to represent the graph; an RDF description for this URI, is considered to represent metadata about the underlying graph. A Tripleset is a new element in RDF statements, previously expressed as triples or quadruples, introduced in the ORDI SG model to describe the association between a statement and an identifiable group of statements. This new term distinguishes the ORDI SG model from several similar, already existing, RDF extensions and the terms associated with them:

• Contexts, as defined in several RDF APIs like Sesame 2.0, YARS and others;
• Datasets, in the way they are defined in SPARQL;
• Named-graphs, in the way they are introduced in [2], implemented in Jena and used in SPARQL.

Given the above extensions, the atomic entity of the ORDI SG tripleset model is a quintuple, composed by the RDF data type primitives - URI, blank node and literal, as follows:

< S, P, O, C, {TS1,…,TSn} >, where:

• S is the subject of a statement; of type URI or blank node;
• P is the predicate of a statement; of type URI;
• O is the object of a statement; of type URI, blank node or literal;
• C is the context of a statement (i.e. Named Graph); of type URI or blank node;
• {TS1, … TSn} is an unordered set of identifiers of the triplesets to which the statement is associated; of type URI or blank node.

More detailed definition of the ORDI SG tripleset model and some examples can be found in the ORDI SG Specification.