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The W3C XQuery language recommendation, based on a hierarchical and ordered document model, supports a wide variety of constructs and use cases. There is a diversity of approaches and strategies for evaluating XQuery expressions, in many cases only dealing with limited subsets of the language. In this paper we describe an implementation approach that(More)
We establish a correspondence between temporal logic and a subset of ATSQL, a temporal extension of SQL-92. In addition, we provide an effective translation from temporal logic to ATSQL that enables a user to write high-level queries which are then evaluated against a space-efficient representation of the database. A reverse translation, also provided in(More)
We propose a new approach to temporal extensions of SQL. Unlike the current proposals, e.g., SQL/Temporal, we use point-based references to time as the basis of our approach. The proposed language| SQL/TP|extends the syntax and semantics of SQL/92 in a very natural way: by adding a single data type to represent a linearly ordered universe of individual time(More)
Conjunctive queries (CQ) are fundamental for ac-cessing description logic (DL) knowledge bases. We study CQ answering in (extensions of) the DL EL, which is popular for large-scale ontologies and underlies the designated OWL2-EL profile of OWL2. Our main contribution is a novel approach to CQ answering that enables the use of standard re-lational database(More)
XML repositories are usually queried both on structure and content. Due to structural heterogeneity of XML, queries are often interpreted approximately and their answers are returned ranked by scores. Computing answer scores in XML is an active area of research that oscillates between pure content scoring such as the well-known tf*idf and taking structure(More)
The use of ontologies for accessing data is one of the most exciting new applications of description logics in databases and other information systems. A realistic way of realising sufficiently scalable on-tology-based data access in practice is by reduction to querying relational databases. In this paper, we describe the combined approach, which(More)