A Main Memory Index Structure to Query Linked Data

A possible approach to query Linked Data combines the actual evaluation of a query with the traversal of data links in order to discover and retrieve potentially relevant data. An implementation of this idea requires approaches that support an efficient and flexible management of temporary, ad hoc data collections that emerge during query execution. However, existing proposals for managing RDF data primarily focus on persistent storage and query execution for large datasets and, thus, are unsuitable in our dynamic scenario which involves many small sets of data. In this paper we investigate main memory data structures to store Linked Data in a query execution system. We discuss the requirements for such a data structure, introduce three strategies that make use of hash table based indexes, and compare these strategies empirically. While this paper focuses on our query execution approach, the discussed data structures can also be applied to other approaches that retrieve Linked Data from remote sources via URI look-ups in order to process this data locally.