Hypertree decompositions, as well as the more powerful generalized hypertree decompositions (GHDs), and the yet more general fractional hypertree decompositions (FHD) are hypergraph decomposition methods successfully used for answering conjunctive queries and for solving constraint satisfaction problems. Every hypergraph H has a width relative to each of these methods: its hypertree width hw(H ), its generalized hypertree width ghw(H ), and its fractional hypertree width fhw(H ), respectively. It is known that hw(H ) ≤ k can be checked in polynomial time for fixed k, while checking ghw(H ) ≤ k is NP-complete for k ≥ 3. The complexity of checking fhw(H ) ≤ k for a fixed k has been open for over a decade.We settle this open problem by showing that checking fhw(H ) ≤ k is NP-complete, even for k = 2. The same construction allows us to prove also the NP-completeness of checking ghw(H ) ≤ k for k = 2. After that, we identify meaningful restrictions which make checking for bounded ghw or fhw tractable or allow for an efficient approximation of the fhw. INTRODUCTION AND BACKGROUNDResearch Challenges Tackled. In this work we tackle computational problems on hypergraph decompositions, which play a prominent role for answering Conjunctive Queries (CQs) and solving Constraint Satisfaction Problems (CSPs), which we discuss below.Many NP-hard graph-based problems become tractable for instances whose corresponding graphs have bounded treewidth. There are, however, many problems for which the structure of an instance is better described by a hypergraph than by a graph, for example, the above mentioned CQs and CSPs. Given that treewidth does not generalize hypergraph acyclicity 1 , proper hypergraph decomposition methods have been developed, in particular, hypertree decompositions (HDs) [27], the more general generalized hypertree decompositions (GHDs) [27], and the yet more general fractional hypertree decompositions (FHDs) [31], and corresponding notions of width of a hypergraph H have been defined: the hypertree width hw(H ), the generalized hypertree width ghw(H ), and the fractional hypertree width fhw(H ), where for every hypergraph H , fhw(H ) ≤ ghw(H ) ≤ hw(H ) holds. Definitions are given in Section 2. A number of highly relevant hypergraph-based problems such as CQ-evaluation and CSP-solving become tractable for classes of instances of bounded hw, ghw, or, fhw. For each of the mentioned types of decompositions it would thus be useful to be able to recognize for each constant k whether a given hypergraph H has corresponding width at most k, and if so, to compute such a decomposition. More formally, for decomposition ∈ {HD, GHD, FHD} and k > 0, we consider the following family of problems: 1 We here refer to the standard notion of hypergraph acyclicity, as used in [50] and [22], where it is called α -acyclicity. This notion is more general than other types of acyclicity that have been introduced in the literature.exists and answer 'no' otherwise. As shown in [27], Check(HD, k) is in Ptime. However, little is known about ...

SPARQL entailment regimes are strongly influenced by the big body of works on ontology-based query answering, notably in the area of Description Logics (DLs). However, the semantics of query answering under SPARQL entailment regimes is defined in a more naive and much less expressive way than the certain answer semantics usually adopted in DLs. The goal of this work is to introduce an intuitive certain answer semantics also for SPARQL and to show the feasibility of this approach. For OWL 2 QL entailment, we present algorithms for the evaluation of an interesting fragment of SPARQL (the so-called well-designed SPARQL). Moreover, we show that the complexity of the most fundamental query analysis tasks (such as query containment and equivalence testing) is not negatively affected by the presence of OWL 2 QL entailment under the proposed semantics.

Mapping relational data to RDF is an important task for the development of the Semantic Web. To this end, the W3C has recently released a Recommendation for the so-called direct mapping of relational data to RDF. In this work, we propose an enrichment of the direct mapping to make it more faithful by transferring also semantic information present in the relational schema from the relational world to the RDF world. We thus introduce expressive identification constraints to capture functional dependencies and define an RDF Normal Form, which precisely captures the classical Boyce-Codd Normal Form of relational schemas.

Rocaglates are natural compounds that have been extensively studied for their ability to inhibit translation initiation. Rocaglates represent promising drug candidates for tumor treatment due to their growth‐inhibitory effects on neoplastic cells. In contrast to natural rocaglates, synthetic analogues of rocaglates have been less comprehensively characterized, but were also shown to have similar effects on the process of protein translation. Here, we demonstrate an enhanced growth‐inhibitory effect of synthetic rocaglates when combined with glucose anti‐metabolite 2‐deoxy‐D‐glucose (2DG) in different cancer cell lines. Moreover, we unravel a new aspect in the mechanism of action of synthetic rocaglates involving reduction of glucose uptake mediated by downregulation or abrogation of glucose transporter GLUT‐1 expression. Importantly, cells with genetically induced resistance to synthetic rocaglates showed substantially less pronounced treatment effect on glucose metabolism and did not demonstrate GLUT‐1 downregulation, pointing at the crucial role of this mechanism for the anti‐tumor activity of the synthetic rocaglates. Transcriptome profiling revealed glycolysis as one of the major pathways differentially regulated in sensitive and resistant cells. Analysis of synthetic rocaglate efficacy in a 3D tissue context with a co‐culture of tumor and normal cells demonstrated a selective effect on tumor cells and substantiated the mechanistic observations obtained in cancer cell lines. Increased glucose uptake and metabolism is a universal feature across different tumor types. Therefore, targeting this feature by synthetic rocaglates could represent a promising direction for exploitation of rocaglates in novel anti‐tumor therapies.

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