A conditional key is a key constraint that is valid in only a part of the data. In this paper, we show how such keys can be mined automatically on large knowledge bases (KBs). For this, we combine techniques from key mining with techniques from rule mining. We show that our method can scale to KBs of millions of facts. We also show that the conditional keys we mine can improve the quality of en...

The equation of state (EOS) is a nontrivial relation linking the thermodynamic variables specifying the state of a physical system . The best known example of EOS is Boyle’s ideal gas law, stating that the pressure of a collection of N noninteracting, pointlike classical particles, enclosed in a volume Ω, grows linearly with the temperature T and the average particle density n = N/Ω. The ideal ...

This article describes the system used by the UGent-IBCN team for participating in the Text Analysis Conference (TAC) 2013 English Entity-Linking task. We kept the overall rule-based workflow of our last year’s submission, but significantly altered individual components. Most importantly, these changes include improved document pre-processing, new ways of candidate selection, and completely red...

We examine the relationship between resource abundance and several indicators of human welfare. Consistent with the existing literature on the relationship between resource abundance and economic growth, we find that resource-abundant countries tend to suffer low levels of human development. While we find no support for a direct link between resources and welfare, there is an indirect link that...

In complex networks it is common to model a network or generate a surrogate network based on the conservation of the network’s degree distribution. We provide an alternative network model based on the conservation of connection density within a set of nodes. This density is measure by the rich–club coefficient. We present a method to generate surrogates networks with a given rich–club coefficie...

We consider the problem of constructing facilities such as hospitals, airports, or malls in a country with a nonuniform population density, such that the average distance from a person's home to the nearest facility is minimized. We review some previous approximate treatments of this problem that indicate that the optimal distribution of facilities should have a density that increases with popu...

A gauge-invariant and hence physically meaningful definition of magnetic helicity density for random fields is proposed, using the Gauss linking formula, as the density of correlated field line linkages. This definition is applied to the random small-scale field in weakly inhomogeneous turbulence, whose correlation length is small compared with the scale on which the turbulence varies. For inho...