We propose a new approach to the treatment of nullvalued attributes in the relational model. The approach is based on the new concept of locally-controlled open world database. A locally-controlled open world dab base permits the definition of portions of a traditional closed world database as open-world. Attributes, part of a relation, or entire relations can be explicitly defined as ‘open” th...

Semi-arid rangelands show much spatial heterogeneity, with some parts producing more and better quality food for herbivores. The concepts of ‘Key Resource’ and ‘Key Resource Area’ have been developed to describe a resource that ‘provides good-quality forage’ and that ‘reduces (inter-)annual variation in forage supply’. Illius and O’Connor (1999) formalised these concepts, arguing that in key re...

A notion of open bisimulation is formulated for the spi calculus, an extension of the πcalculus with cryptographic primitives. This notion of open bisimulation is based on the so-called hedged bisimulation, due to Borgström and Nestmann. Open bisimulation is shown to be sound with respect to hedged bisimulation, and futher, open bisimilarity is shown to be a congruence relation on finite spi pr...

In contrast with traditional relation extraction, which only considers a fixed set of relations, Open Information Extraction (Open IE) aims at extracting all types of relations from text. Because of data sparseness, Open IE systems typically ignore lexical information, and instead employ parse trees and Part-of-Speech (POS) tags. However, the same syntactic structure may correspond to different...

It is well known that members of families of polynomials, that are orthogonal with respect to an inner product determined by a nonnegative measure on the real axis, satisfy a three-term recursion relation. Analogous recursion formulas are available for orthogonal Laurent polynomials with a pole at the origin. This paper investigates recursion relations for orthogonal rational functions with arb...

Let C be a class of relational structures. We denote by fC(n) the number of structures in C over the labeled set {0, . . . , n − 1}. For any C definable in monadic second order logic with unary and binary relation symbols only, E. Specker and C. Blatter showed that for every m ∈ N, the function fC satisfies a linear recurrence relation modulo m, and hence it is ultimately periodic modulo m. The...

Open IE usually has been studied for English which of one of subject-verb-object(SVO) languages where a relation between two entities tends to occur in order of entity-relational phrase-entity within a sentence. However, in SOV languages, two entities occur before the relational phrase so that the subject and the relation have a long distance. The conventional methods for Open IE mostly dealing...