RDF(S) Reasoning and Query Answering in a Peer-to-Peer Framework
The current centralized RDF databases have limitations both in their failure tolerance and in their scalability, and their limited capacities will become incapable of handling the anticipated load of Semantic Web data available in the future. Thus the efficient distributed databases are a necessary precondition for the acceptance of the Semantic Web. Peer-to-Peer networks can offer a foundation layer of such distributed database.
The current research at the frontier of Peer-to-Peer networks and Semantic Web is based on structured Peer-to-Peer networks, in particular a ring-shaped distributed hash table (DHT) is used for the storage and querying of RDF data at Internet scale. The basic idea is to store each triple at three locations (nodes) on the DHT ring determined by calculating the hash value of the subject, predicate, and object. The application of uniform hashing functions in DHTs to map applications keys to their identifier space achieves efficient discovery for exact keys and good storage load balancing, but sacrifices the order relationship of the keys. Keys which are semantically close at the application level are heavily fragmented in a DHT, and thus spoils the efficiency of range queries, conjunctive queries, and updates on related attributes.
My work is focus on design and development of a Peer-to-Peer networks that cluster semantically close data items, which is a precondition for efficient processing of conjunctive queries, range queries, and reasoning on RDF data.
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Related Publications
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Liaquat Ali, Thomas Janson, Georg Lausen, and Christian Schindelhauer:
Effects of Network Structure Improvement on Distributed RDF Querying [ .pdf ]
6th International Conference on Data Management in Cloud, Grid and P2P Systems (Globe 2013). Prague (Czech Republic). -
Liaquat Ali, Georg Lausen:
3rdf: Evaluating SPARQL Subqueries Over P2P Overlay Networks
11th International Workshop on Web Semantics (WebS 2012), in conjunction with the 23rd International Conference on Database and Expert Systems Applications (DEXA 2012). Vienna (Austria). -
Liaquat Ali, Thomas Janson, Georg Lausen:
3rdf: Storing and Querying RDF Data on top of the 3nuts Overlay Network[ .pdf ]
10th International Workshop on Web Semantics (WebS 2011), in conjunction with the 22nd International Conference on Database and Expert Systems Applications (DEXA 2011). Toulouse (France).