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Found 6 papers, 0 papers with code
Characterising Fixed Parameter Tractability of Query Evaluation over Guarded TGDs
We study the parameterized complexity of evaluating Ontology Mediated Queries (OMQs) based on Guarded TGDs (GTGDs) and Unions of Conjunctive Queries (UCQs), in the case where relational symbols have unrestricted arity and where the parameter is the size of the OMQ.
Answer Counting under Guarded TGDs
We study the complexity of answer counting for ontology-mediated queries and for querying under constraints, considering conjunctive queries and unions thereof (UCQs) as the query language and guarded TGDs as the ontology and constraint language, respectively.
Databases
From Conjunctive Queries to Instance Queries in Ontology-Mediated Querying
We consider ontology-mediated queries (OMQs) based on expressive description logics of the ALC family and (unions) of conjunctive queries, studying the rewritability into OMQs based on instance queries (IQs).
When is Ontology-Mediated Querying Efficient?
We further study the complexity of the meta problem of deciding whether a given OMQ is equivalent to an OMQ of bounded tree width, providing several completeness results that range from NP to 2ExpTime, depending on the DL used.
The Limits of Efficiency for Open- and Closed-World Query Evaluation Under Guarded TGDs
For querying in the presence of constraints, we consider classes of constraint-query specifications (CQSs) that bundle a set of constraints with an actual query.
A Practical Acyclicity Notion for Query Answering over Horn-SRIQ Ontologies
Conjunctive query answering over expressive Horn Description Logic ontologies is a relevant and challenging problem which, in some cases, can be addressed by application of the chase algorithm.
