Query answering under existential rules — implications with existential quantifiers in the head — is known to be decidable when imposing restrictions on the rule bodies such as frontier-guardedness [BLM10, BLMS11]. Query answering is also decidable for description logics [Baa03], which further allow disjunction and functionality constraints (assert that certain relations are functions); however...

This paper proposes a new semantics that characterizes the time and/or situation dependencies of properties, together with the ontological notion of existential rigidity. For this purpose, we present order-sorted tempo-situational logic (OSTSL) with rigid/anti-rigid sorts and an existential predicate. In this logic, rigid/anti-rigid sorted terms enable the expressions for sortal properties, and...

An existential theorem, for the specification or implementation of hardware, states that for any inputs there must exist at least one output which is consistent with it. It is proved to prevent an inconsistent model being produced and it is required to formally import the verification result from one verification system to another system. In this paper, we investigate the verification of the ex...

A structure M is pregeometric if the algebraic closure is a pregeometry in all M ′ elementarily equivalent to M . We define a generalisation: structures with an existential matroid. The main examples are superstable groups of U-rank a power of ω and d-minimal expansion of fields. Ultraproducts of pregeometric structures expanding a field, while not pregeometric in general, do have an unique exi...

One source of complexity in the μ-calculus is its ability to specify an unbounded number of switches between universal (AX) and existential (EX) branching modes. We therefore study the problems of satisfiability, validity, model checking, and implication for the universal and existential fragments of the μ-calculus, in which only one branching mode is allowed. The universal fragment is rich eno...

Humans live out their lives knowing that their own death is inevitable; that their most cherished beliefs and values, and even their own identities, are uncertain; that they face a bewildering array of choices; and that their private subjective experiences can never be shared with another human being. This knowledge creates five major existential concerns: death, isolation, identity, freedom, a...

We give a solution to the succinctness problem for the size of first-order rewritings of conjunctive queries in ontologybased data access with ontology languages such as OWL 2 QL , linear Datalog± and sticky Datalog±. We show that positive existential and nonrecursive datalog rewritings, which do not use extra non-logical symbols (except for intensional predicates in the case of datalog rewriti...

The straightforward elimination of union types is known to break subject reduction, and for some extensions of the lambda-calculus, to break strong normalization as well. Similarly, the straightforward elimination of implicit existential types breaks subject reduction. We propose elimination rules for union types and implicit existential quantification which use a form call-by-value issued from...

Traditional inconsistency-tolerent query answering in ontology-based data access relies on selecting maximal components of an ABox/database which are consistent with the ontology. However, some rules in ontologies might be unreliable if they are extracted from ontology learning or written by unskillful knowledge engineers. In this paper we present a framework of handling inconsistent existentia...

Research suggests that addressing dying patients' existential concerns can improve their quality of life. We aimed to illuminate dying patients' existential concerns about the impending death through a descriptive analysis of semistructured interviews with 17 patients in Danish hospices. The main findings demonstrated how the patients faced the imminent death without being anxious of death but ...