ON THE EXPRESSIVE POWER OF INFINITE TEMPORAL DATABASES

We discuss different techniques for representing infinite temporal data. There are two basic approaches: A procedural description, as used in production systems, and represented, in this paper, by a version of Datalog. The second approach is a more declarative method, using some form of temporal logic programming. We examine several versions of each approach, and compare their expressive power, i.e., what temporal data each formalism can capture.Information Systems Working Papers Serie

Natural disasters and indicators of social cohesion

Do adversarial environmental conditions create social cohesion? We provide new answers to this question by exploiting spatial and temporal variation in exposure to earthquakes across Chile. Using a variety of methods and controlling for a number of socio-economic variables, we find that exposure to earthquakes has a positive effect on several indicators of social cohesion. Social cohesion increases after a big earthquake and slowly erodes in periods where environmental conditions are less adverse. Our results contribute to the current debate on whether and how environmental conditions shape formal and informal institutions

Looking through the 'window of opportunity': is there a new paradigm of podiatry care on the horizon in early rheumatoid arthritis?

Over the past decade there have been significant advances in the clinical understanding and care of rheumatoid arthritis (RA). Major paradigm changes include earlier disease detection and introduction of therapy, and 'tight control' of follow-up driven by regular measurement of disease activity parameters. The advent of tumour necrosis factor (TNF) inhibitors and other biologic therapies have further revolutionised care. Low disease state and remission with prevention of joint damage and irreversible disability are achievable therapeutic goals. Consequently new opportunities exist for all health professionals to contribute towards these advances. For podiatrists relevant issues range from greater awareness of current concepts including early referral guidelines through to the application of specialist skills to manage localised, residual disease activity and associated functional impairments. Here we describe a new paradigm of podiatry care in early RA. This is driven by current evidence that indicates that even in low disease activity states destruction of foot joints may be progressive and associated with accumulating disability. The paradigm parallels the medical model comprising early detection, targeted therapy, a new concept of tight control of foot arthritis, and disease monitoring

On the Expressive Power of Infinite Temporal Databases

We discuss different techniques for representing infinite temporal data. There are two basic approaches: A procedural description, as used in production systems, and represented, in this paper, by a version of Datalog. The second approach is a more declarative method, using some form of temporal logic programming. We examine sev-eral versions of each approach, and compare their expressive power, i.e., what temporal data each formalism can capture.

A Representation Independent Language for Planar Spatial Databases with Euclidean Distance

Abstract. Linear constraint databases and query languages are appropriate for spatial database applications. Not only the data model is natural to represent a large portion of spatial data suchas in GIS systems, but also there exist efficient algorithms for the core operations in the query languages. However, an important limitation of the linear constraint data model is that it cannot model constructs such as “Euclidean distance. ” A previous attempt to expend linear constraint languages withthe ability to express Euclidean distance, by Kuijpers, Kuper, Paredaens, and Vandeurzen is to adapt two fundamental Euclidean constructions withruler and compass in a first order logic over points. The language, however, requires the input database to be encoded in an ad hoc LPC representation so that the logic operations can apply. This causes a problem that sometimes queries in their language may depend on the encoding and thus do not have any natural meaning. In this paper, we propose an alternative approach and develop an algebraic language in which the traditional operators and Euclidean constructions work directly on the data represented by “semi-circular ” constraints. By avoiding the encoding step, our language do not suffer from this problem. We show that the language is closed under these operations.