The ρ-Operator : Enabling Querying for Semantic Associations on the Semantic Web

Semantic Associations are a class of complex relationships between entities that capture a connectivity of entities or a pattern of entities and relationships between them based on a specific notion of an isomorphism called ρ-isomorphism. In an RDF graph data model, they may represented as sequences (i.e. paths) between entities, networks of sequences, or a subgraph containing ρ-isomorphic sequences. Capturing such relationships based on their structural properties, allows us to define them as types that may be returned as results of a query. Such a capability, while lacking in most RDF query languages, is essential in supporting many of the tasks found in analytical domains such as national security and business intelligence. In these domains, investigative tasks are often focused on detecting such complex associations that may be buried deep in the data. This paper presents a formalization of Semantic Associations for the RDF data model. It also shows how querying for such relationships may be enabled on the Semantic Web, through the use of an operator ρ. Finally, it discusses two approaches for implementing the ρ operator. One of the approaches is based on building upon current RDF query languages, allowing the reuse of existing infrastructure.