Joachim Kröger

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With the substantial change of declarative query languages from plain SQL to the so-called \object SQLs", in particular OQL, there has surprisingly been not much change in the way problems of query representation and optimization for such languages are tackled. We identify some of the diiculties pure algebraic approaches experience when facing object models(More)
The conceptual development of the rule{based component of the CROQUE query rewrite and optimization system led to the derivation of an ordering of the rules present in the rule base according to their \optimization potential" in order to increase the eeciency of the logical term rewriting 5]. This heuristic may indeed be used for any other rule{based(More)
One of the hard aspects of query optimization is the query rewriting process. Using rewrite rules, a given query will be transformed into an equivalent execution plan that is cheaper than the straightforwardly assigned plan according to some cost model. Finding the cheapest of all equivalent execution plans is a challenge since the rewriting of complex(More)