A Data warehouse is a tool that is used by big companies, and it gathers data coming from different sources. The main goal of a data warehouse is not only to store data, but also to help companies to make decisions. The huge volume of data makes processing queries complex and time-consuming. In order to solve this problem, the materialization of views is suggested as a solution to improve the p...

Sommario Logical design of data warehouses (DW) encompasses the sequence of steps which, given a core work-load, determine the logical scheme for the DW. A key step in logical design is view materialization. In this paper we propose an original approach to materialization in which the workload is characterized by the presence of complex queries represented by Nested Generalized Projection/Selec...

Selective materialization of intermediate query results as views is an effective method for improving query performance. In this paper, we extend this technique to adaptively partition views based on the access patterns of a workload. That is, we collect information about the selection conditions of queries at runtime and utilize this information to determine fragment boundaries for the initial...

A data warehouse uses multiple materialized views to efficiently process a given set of queries. These views are accessed by read-only queries and need to be maintained after updates to base tables. Due to the space constraint and maintenance cost constraint, the materialization of all views is not possible. Therefore, a subset of views needs to be selected to be materialized. The problem is NP...

Materialization is an important reasoning service for applications built on theWeb Ontology Language (OWL). To make materialization efficient in practice, current research focuses on deciding tractability of an ontology language and designing parallel reasoning algorithms. However, some well-known large-scale ontologies, such as YAGO, have been shown to have good performance for parallel reason...

This paper presents a novel approach, QSMat, for efficient RDF data stream querying with flexible query-based materialization. Previous work accelerates either the maintenance of a stream window materialization or the evaluation of a query over the stream. QSMat exploits knowledge of a given query and entailment rule-set to accelerate window materialization by avoiding inferences that provably ...

In database terminology, a view is a query that is stored and given a name by which it can be used in other queries. Views are an established technique for virtually restructuring data, classes, and schemata so as to meet the needs of specific applications or users, for integrating heterogeneous and distributed systems (for example, data warehouse systems), and for achieving interoperability by...

ion Refinement Markus Brenner and Birte Glimm University of Ulm, Germany, [email protected] Abstract. Abstraction refinement is a recently introduced technique Abstraction refinement is a recently introduced technique which allows for reducing materialization of an ontology with a large ABox to materialization of a smaller (compressed) ‘abstraction’ of this ontology. In this p...

The view mechanism can provide the user with an appropriate portion of database through data filtering and integration. Views are often materialized for query performance improvement, and in that case, their consistency needs to be maintained against the updates of the underlying data. They can be either recomputed or incrementally refreshed by reflecting only the relevant updates. With the eme...

Abstraction refinement is a recently introduced technique which allows for reducing materialization of an ontology with a large ABox to materialization of a smaller (compressed) ‘abstraction’ of this ontology. Although this approach is sound for the very expressive language SROIQ, so far it was proved to be complete only for Horn ALCHOI ontologies. In this paper we propose an extension of this ...