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Although temporal databases have received considerable attention as a topic for research , little work in the area has paid attention to the concurrency control mechanisms that might be employed in temporal databases. This paper describes how the notion of the current time | also called`now' | in valid-time databases can cause standard seriali-sation theory(More)
This paper presents a new approach to data integration, which combines the previous approaches of local as view (LAV) and global as view (GAV) into a single method we term both as view (BAV). Our method is based on the use of reversible transformation sequences, and combines the respective advantages of GAV and LAV. In particular, in common with GAV,(More)
Several methodologies for integrating database schemas have been proposed in the literature, using various common data models (CDMs). As part of these methodologies transformations have been defined that map between schemas which are in some sense equivalent. This paper describes a general framework for formally underpinning the schema transformation(More)
XML is fast becoming the standard for information exchange on the Internet. As such, information expressed in XML will need to be integrated with existing information systems, which are mostly based on structured data models such as relational, object-oriented or ob-ject/relational data models. This paper shows how our previous framework for integrating(More)
The loose and dynamic association between peers in a peer-to-peer integration has meant that, to date, implementations of peer-to-peer systems have been based on the exchange of files identified with a very limited set of attributes, and no schema is used to describe the data within those files. This paper extends an existing approach to data integration,(More)
This paper describes view generation and view optimisation in the AutoMed heterogeneous data integration framework. In AutoMed, schema integration is based on the use of reversible schema transformation sequences. We show how views can be generated from such sequences, for global-as-view (GAV), local-as-view (LAV) and GLAV query processing. We also present(More)
This paper presents a new approach to schema evolution, which c o m bines the activities of schema integration and schema evolution into one framework. In previous work we h a ve developed a general framework to support schema transformation and integration in heterogeneous database architectures. Here we s h o w h o w this framework also readily supports(More)
We review attempts at defining a general extension to the relational algebra to incl udc temporal semantics, and dcfinc two temporal operators to achieve a temporal relational algebra with a close correspondence to temporal logic using since and until. We then dcmonstratc how this temporal relational algebra may IO ;I limited extent be encoded in standard(More)