Nicole Schweikardt

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We introduce an extension of the XQuery language, FluX, that supports event-based query processing and the conscious handling of main memory buffers. Purely event-based queries of this language can be executed on streaming XML data in a very direct way. We then develop an algorithm that allows to efficiently rewrite XQueries into the event-based FluX(More)
Data exchange deals with the following problem: given an instance over a source schema, a specification of the relationship between the source and the target,and dependencies on the target, construct an instance over a target schema that satisfies the given relationships and dependencies. Recently - for data exchange settings without target dependencies -(More)
A language L over an alphabet A is said to have a neutral letter if there is a letter e ∈ A such that inserting or deleting e’s from any word in A∗ does not change its membership or non-membership in L. The presence of a neutral letter affects the definability of a language in firstorder logic. It was conjectured that it renders all numerical predicates(More)
We consider a scenario where we want to query a large dataset that is stored in external memory and does not fit into main memory. The most constrained resources in such a situation are the size of the main memory and the number of random accesses to external memory. We note that sequentially streaming data from external memory through main memory is much(More)
Succinctness is a natural measure for comparing the strength of different logics. Intuitively, a logic L/sub 1/ is more succinct than another logic L/sub 2/ if oil properties that can be expressed in L/sub 2/ can be expressed in L/sub 1/ by formulas of (approximately) the same size, but some properties can be expressed in L/sub 1/ by (significantly) smaller(More)
We consider a scenario where we want to query a large dataset that is stored in external memory and does not fit into main memory. The most constrained resources in such a situation are the size of the main memory and the number of random accesses to external memory. We note that sequentially streaming data from external memory through main memory is much(More)
XML has established itself as the ubiquitous format for data exchange on the Internet. An imminent development is that of streams of XML data being exchanged and queried. Data management scenarios where XQuery [11] is evaluated on XML streams are becoming increasingly important and realistic, e.g. in e-commerce settings. Naturally, query engines employed(More)
We study the expressiveness and the complexity of static analysis of extended conjunctive regular path queries (ECRPQs), introduced by Barceló et al. (PODS ’10). ECRPQs are an extension of conjunctive regular path queries (CRPQs), a well-studied language for querying graph structured databases. Our first main result shows that query containment and(More)