Conjunctive query answering over unrestricted OWL 2 ontologies
Conjunctive Query (CQ) answering is a primary reasoning task over knowledge bases. However, when considering expressive description logics, query answering can be computationally very expensive; reasoners for CQ answering, although heavily optimized, often sacrifice expressive power of the input ont...
| Main Authors: | , , |
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| Format: | Journal article |
| Language: | English |
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IOS Press
2023
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| _version_ | 1826312462273609728 |
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| author | Igne, F Germano, S Horrocks, I |
| author_facet | Igne, F Germano, S Horrocks, I |
| author_sort | Igne, F |
| collection | OXFORD |
| description | Conjunctive Query (CQ) answering is a primary reasoning task over knowledge bases. However, when considering expressive description logics, query answering can be computationally very expensive; reasoners for CQ answering, although heavily optimized, often sacrifice expressive power of the input ontology or completeness of the computed answers in order to achieve tractability and scalability for the problem. In this work, we present a hybrid query answering architecture that combines various services to provide a CQ answering service for OWL. Specifically, it combines scalable CQ answering services for tractable languages with a CQ answering service for a more expressive language approaching the full OWL 2. If the query can be fully answered by one of the tractable services, then that service is used, to ensure maximum performance. Otherwise, the tractable services are used to compute lower and upper bound approximations. The union of the lower bounds and the intersection of the upper bounds are then compared. If the bounds do not coincide, then the “gap” answers are checked using the “full” service. These techniques led to the development of two new systems: (i) RSAComb, an efficient implementation of a new tractable answering service for RSA (role safety acyclic) (ii) ACQuA, a reference implementation of the proposed hybrid architecture combining RSAComb, PAGOdA, and HermiT to provide a CQ answering service for OWL. Our extensive evaluation shows how the additional computational cost introduced by reasoning over a more expressive language like RSA can still provide a significant improvement compared to relying on a fully-fledged reasoner. Additionally, we show how ACQuA can reliably match the performance of PAGOdA, a state-of-the-art CQ answering system that uses a similar approach, and can significantly improve performance when PAGOdA extensively relies on the underlying fully-fledged reasoner. |
| first_indexed | 2024-03-07T08:29:19Z |
| format | Journal article |
| id | oxford-uuid:8888bb8c-8775-4023-b6a1-4e62f9e5567d |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:29:19Z |
| publishDate | 2023 |
| publisher | IOS Press |
| record_format | dspace |
| spelling | oxford-uuid:8888bb8c-8775-4023-b6a1-4e62f9e5567d2024-03-04T11:54:08ZConjunctive query answering over unrestricted OWL 2 ontologiesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:8888bb8c-8775-4023-b6a1-4e62f9e5567dEnglishSymplectic ElementsIOS Press2023Igne, FGermano, SHorrocks, IConjunctive Query (CQ) answering is a primary reasoning task over knowledge bases. However, when considering expressive description logics, query answering can be computationally very expensive; reasoners for CQ answering, although heavily optimized, often sacrifice expressive power of the input ontology or completeness of the computed answers in order to achieve tractability and scalability for the problem. In this work, we present a hybrid query answering architecture that combines various services to provide a CQ answering service for OWL. Specifically, it combines scalable CQ answering services for tractable languages with a CQ answering service for a more expressive language approaching the full OWL 2. If the query can be fully answered by one of the tractable services, then that service is used, to ensure maximum performance. Otherwise, the tractable services are used to compute lower and upper bound approximations. The union of the lower bounds and the intersection of the upper bounds are then compared. If the bounds do not coincide, then the “gap” answers are checked using the “full” service. These techniques led to the development of two new systems: (i) RSAComb, an efficient implementation of a new tractable answering service for RSA (role safety acyclic) (ii) ACQuA, a reference implementation of the proposed hybrid architecture combining RSAComb, PAGOdA, and HermiT to provide a CQ answering service for OWL. Our extensive evaluation shows how the additional computational cost introduced by reasoning over a more expressive language like RSA can still provide a significant improvement compared to relying on a fully-fledged reasoner. Additionally, we show how ACQuA can reliably match the performance of PAGOdA, a state-of-the-art CQ answering system that uses a similar approach, and can significantly improve performance when PAGOdA extensively relies on the underlying fully-fledged reasoner. |
| spellingShingle | Igne, F Germano, S Horrocks, I Conjunctive query answering over unrestricted OWL 2 ontologies |
| title | Conjunctive query answering over unrestricted OWL 2 ontologies |
| title_full | Conjunctive query answering over unrestricted OWL 2 ontologies |
| title_fullStr | Conjunctive query answering over unrestricted OWL 2 ontologies |
| title_full_unstemmed | Conjunctive query answering over unrestricted OWL 2 ontologies |
| title_short | Conjunctive query answering over unrestricted OWL 2 ontologies |
| title_sort | conjunctive query answering over unrestricted owl 2 ontologies |
| work_keys_str_mv | AT ignef conjunctivequeryansweringoverunrestrictedowl2ontologies AT germanos conjunctivequeryansweringoverunrestrictedowl2ontologies AT horrocksi conjunctivequeryansweringoverunrestrictedowl2ontologies |