Markus Kröll

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With the steadily increasing amount of incomplete data on the web, the need for partial matching as an extension of Conjunctive Queries (CQs) is gaining more and more importance. Therefore, the OPTIONAL operator is a crucial feature in the semantic web query language SPARQL, and has also been studied for arbitrary relational vocabulary recently [3].(More)
Several computational problems of abstract argumentation frameworks (AFs) such as skeptical and credulous reasoning, existence of a non-empty extension, verification, etc. have been thoroughly analyzed for various semantics. In contrast, the enumeration problem of AFs (i.e., the problem of computing all extensions according to some semantics) has been left(More)
2 τ-adic Expansions 3 2.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 Properties of τ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3 Digit Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.4 Optimality . . . . . . . . . . . . . . . . . . . . . . .(More)
Complexity theory provides a wealth of complexity classes for analyzing the complexity of decision and counting problems. Despite the practical relevance of enumeration problems, the tools provided by complexity theory for this important class of problems are very limited. In particular, complexity classes analogous to the polynomial hierarchy and an(More)
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