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Querying Heterogeneous Property Graph Data Sources based on a Unified Conceptual View

With the great success of NoSQL (Not only SQL) databases, data becomes more heterogeneous than ever. Hence, it is essential to provide solutions to integrate such heterogeneous databases and facilitate accessing them. This paper proposes an Ontology Based Data Access (OBDA) approach to query NoSQL property graph databases using SPARQL language. This allows users to access diverse data sources with the same query through a unified conceptual view (ontology). The proposed work goes through an offline phase to map the property graph data model to a unified ontology model. This is done by proposing hybrid relational graph algebra expressions. Then, an online phase starts when the user submits a SPARQL query. The submitted query is translated into the property graph declarative query language, Cypher. The translated query is then executed on the target property graph database and query results are presented to users in a unified format.