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We show that relational algebra calculations for incomplete databases, probabilistic databases, bag semantics and why-provenance are particular cases of the same general algorithms involving semirings. This further suggests a comprehensive provenance representation that uses semirings of polynomials. We extend these considerations to datalog and semirings(More)
We present a new principle for the development of database query languages that the primitive operations should be organized around types. Viewing a relational database as consisting of sets of records, this principle dictates that we should investigate separately operations for records and sets. There are two immediate advantages of this approach, which is(More)
The integration of heterogeneous data sources and software systems is a major issue in the biomed ical community and several approaches have been explored: linking databases, "on-thefly" integration through views, and integration through warehousing. In this paper we report on our experiences with two systems that were developed at the University of(More)
We state and solve the query reformulation problem for XML publishing in a general setting that allows mixed (XML and relational) storage for the proprietary data and exploits redundancies (materialized views, indexes and caches) to enhance performance. The correspondence between published and proprietary schemas is specified by views in both directions,(More)
Let &#931;<inf>1</inf>, &#931;<inf>2</inf> be two schemas, which may overlap, <i>C</i> be a set of constraints on the joint schema &#931;<inf>1</inf> &#8746; &#931;<inf>2</inf>, and <i>q</i><inf>1</inf> be a &#931;<inf>1</inf>-query. An <b>(equivalent) reformulation</b> of <i>q</i><inf>1</inf> in the presence of <i>C</i> is a &#931;<inf>2</inf>-query,(More)
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We study issues that arise in programming with primitive recursion over non-free datatypes such as lists, bags and sets. Programs written in this style can lack a meaning in the sense that their outputs may be sensitive to the choice of input expression. We are, thus, naturally led to a set-theoretic denotational semantics with partial functions. We set up(More)
Machiavelli is a polymorphically typed programming language in the spirit of ML, but supports an extended method of type inferencing that makes its polymorphism more general and appropriate for database applications. In particular, a function that selects a field &fnof; of a records is polymorphic in the sense that it can be applied to any record which(More)