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Instance Store Database Support for Reasoning over Individuals

Instance Store Database Support for Reasoning over Individuals. S Bechhofer, I Horrocks, D Turi. Instance Store - Database Support for Reasoning over Individuals . http://instancestore.man.ac.uk/instancestore.pdf Dumitru Roman. Outline. Introduction Instance Store Implementation

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Instance Store Database Support for Reasoning over Individuals

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  1. Instance StoreDatabase Support for Reasoning over Individuals S Bechhofer, I Horrocks, D Turi.Instance Store - Database Support for Reasoning over Individuals.http://instancestore.man.ac.uk/instancestore.pdf Dumitru Roman

  2. Outline • Introduction • Instance Store • Implementation • Comparisons & Evaluation

  3. Introduction • Description Logic (DL): T-Box & A-Box. • More expressive DL languages - distinction between the T- and A-Box collapses. • A full DL A-box allows us to make assertions about individuals of the form I € D and P(i, j) for individuals i and j, arbitrary concept descriptions D and properties (binary relationships) P. We can then query the A-box with queries such as: • Retrieval Which individuals occurring in the assertions are instances of some concept description Q? • Realization Given an individual i, what are the most specific concepts C in the T-box that i is an instance of? • Answering such queries requires full A-box reasoning, a task that is known to be difficult in the presence of expressive languages for the T-box • an alternative approach – the instance store – providing a limited, yet effective form of A-box reasoning. • The paper discusses implementation strategies for an instance store using a combination of relational database and DL reasoner.

  4. well known technique for implementing an instance store - simply treat individuals as primitive concept definitions and add new primitive concepts “pseudo-individuals” for each individual. Retrieval then simply involves classifying the query and returning all individuals such that their associated “pseudo-individuals”lie below the query in the concept hierarchy. Problem - with realistic knowledge bases likely to run into millions of instances,such an approach is unlikely to scale. Solution - The instances and their relationship with concepts are stored in the database, while the reasoner deals purely with T-Box functionality. Retrieving individuals is then a combination of query against that database and subsumption and classification requests to the reasoner. Instance Store

  5. Instance Store - Architecture

  6. Instance Store – retrieval algorithm

  7. Instance Store - Implementation • Basic Strategy • stores minimal information in the database, and • relies on the reasoner to provide subsumption testing and hierarchy information. • Classified Descriptions • Cache the classification of each asserted and retrieved description.

  8. Comparisons & Evaluation

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