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This paper investigates the relationship between automataand tableau-based inference procedures for description logics. To be more precise, we develop an abstract notion of what a tableau-based algorithm is, and then show, on this abstract level, how tableau-based algorithms can be converted into automata-based algorithms. In particular, this allows us to(More)
Two prominent families of algorithms for the satisfiability test of DLs are automatabased algorithms (see e.g. [6]), which translate a concept C into an automaton AC accepting all (abstractions of) models for C, and tableau algorithms (TAs) [2], which incrementally create a tree-shaped (pre-) model for C using a set of completion rules. In short, the(More)
Access control is crucial also for the Semantic Web. Technologies and Standards from the Semantic Web Community itself provide powerful means to model access control definitions and automatically reason about them. We extend Hierarchical Role Based Access Control by a class hierarchy of the accessed objects and give it the name RBAC-CH. We present a concept(More)
In the area of Description Logic (DL), both tableau-based and automata-based algorithms are frequently used to show decidability and complexity results for basic inference problems such as satisfiability of concepts. Whereas tableau-based algorithms usually yield worst-case optimal algorithms in the case of PSpace-complete logics, it is often very hard to(More)
Tree automata are often used for satisfiability testing in the area of description logics, which usually yields ExpTime complexity results. We examine conditions under which this result can be improved, and we define two classes of automata, called segmentable and weakly-segmentable, for which emptiness can be decided using space logarithmic in the size of(More)
Nowadays, apps provide support for various simple tasks. They are easy to use and highly usable. However, future apps should support more complex workflows especially when trying to enter the professional business world. They need to provide higher reusability and composability in order to make them suitable for complex and alterable workflows that are(More)