Parallel-Correctness and Transferability for Conjunctive Queries
نویسندگان
چکیده
منابع مشابه
Parallel-Correctness and Containment for Conjunctive Queries with Union and Negation
Single-round multiway join algorithms first reshuffle data over many servers and then evaluate the query at hand in a parallel and communicationfree way. A key question is whether a given distribution policy for the reshuffle is adequate for computing a given query, also referred to as parallel-correctness. This paper extends the study of the complexity of parallel-correctness and its constitue...
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Query containment for conjunctive queries is the problem of checking whether a query q is contained in another query q′ with respect to a given Description Logic schema S. It is known that query containment can also be used to answer queries. Query containment is important in many areas, including information integration, query optimisation, and reasoning about Entity-Relationship diagrams, whi...
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A query Q is said to be effectively bounded if for all datasets D, there exists a subset DQ of D such that Q(D) = Q(DQ), and the size of DQ and time for fetching DQ are independent of the size of D. The need for studying such queries is evident, since it allows us to compute Q(D) by accessing a bounded dataset DQ, regardless of how big D is. This paper investigates effectively bounded conjuncti...
متن کاملDynamic Conjunctive Queries
The article investigates classes of queries maintainable by conjunctive queries (CQs) and their extensions and restrictions in the dynamic complexity framework of Patnaik and Immerman. Starting from the basic language of quantifier-free conjunctions of positive atoms, it studies the impact of additional operators and features — such as union, atomic negation and quantification — on the dynamic ...
متن کاملConjunctive Queries for EL with Role Composition
EL is a rather expressive description logic (DL) that still admits polynomial time inferencing for many reasoning tasks. Conjunctive queries are an important means for expressive querying of DL knowledge bases. In this paper, we address the problem of computing conjunctive query entailment for EL knowledge bases. As it turns out, querying unrestricted EL is actually undecidable, but we identify...
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ژورنال
عنوان ژورنال: Journal of the ACM
سال: 2017
ISSN: 0004-5411,1557-735X
DOI: 10.1145/3106412