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Recently, it has been shown that the small description logic (DL) EL, which allows for conjunction and existential restrictions, has better algorithmic properties than its counterpart FL 0 , which allows for conjunction and value restrictions. Whereas the subsumption problem in FL 0 becomes already intractable in the presence of acyclic TBoxes, it remains… (More)

In the area of Description Logic (DL) based knowledge representation, research on reasoning w.r.t. general terminologies has mainly focused on very expressive DLs. Recently, though, it was shown for the DL EL, providing only the constructors conjunction and existential restriction, that the subsumption problem w.r.t. cyclic terminologies can be decided in… (More)

We extend the description logic EL ++ with reflexive roles and range restrictions, and show that subsumption remains tractable if a certain syntactic restriction is adopted. We also show that subsumption becomes PSpace-hard (resp. undecidable) if this restriction is weakened (resp. dropped). Additionally, we prove that tractability is lost when symmetric… (More)

- Sebastian Brandt, Orr Fischer, Juho Hirvonen, Barbara Keller, Tuomo Lempiäinen, Joel Rybicki +2 others
- STOC
- 2016

We show that any randomised Monte Carlo distributed algorithm for the Lovász local lemma requires Ω(log log n) communication rounds, assuming that it finds a correct assignment with high probability. Our result holds even in the special case of d = O(1), where d is the maximum degree of the dependency graph. By prior work, there are distributed algorithms… (More)

—We study consistent migration of flows, with special focus on software defined networks. Given a current and a desired network flow configuration, we give the first polynomial-time algorithm to decide if a congestion-free migration is possible. However, if all flows must be integer or are unsplittable, this is NP-hard to decide. A similar problem is… (More)

Recently, it was shown for the DL EL that subsumption and instance problem w.r.t. cyclic terminologies can be decided in polynomial time. In this paper, we show that both problems remain tractable even when admitting general concept inclusion axioms and simple role inclusion axioms. 1 Motivation In the area of DL based knowledge representation, the utility… (More)

Matching problems in Description Logics are theoretically well understood, with a variety of algorithms available for different DLs. Nevertheless, still no implementation of a general matching algorithm exists. The present paper presents an implementation of an existing matching algorithm for the DL ALE and shows first results on benchmarks w.r.t. randomly… (More)

Updating network flows in a real-world setting is a nascent research area, especially with the recent rise of Software Defined Networks. While augmenting <i>s-t</i> flows of a single commodity is a well-understood concept, we study updating flows in a multi-commodity setting: Given a directed network with flows of different commodities, how can the capacity… (More)

There has been major progress both in description logics and ontology design since SNOMED was originally developed. The emergence of the standard Web Ontology language in its latest revision, OWL 1.1 is leading to a rapid proliferation of tools. Combined with the increase in computing power in the past two decades, these developments mean that many of the… (More)