Redevelopment of an industrial case study using Event-B and Rodin

CDIS is a commercial air traffic information system that was developed using formal methods 15 years ago by Praxis, and it is still in operation today. This system is an example of an industrial scale system that has been developed using formal methods. In particular, the functional requirements of the system were specified using VVSL -- a variant of VDM. A subset of the original specification has been chosen to be reconstructed on the Rodin platform based on the new Event-B formalism. The goal of our reconstruction was to overcome three key difficulties of the original formalisation, namely the difficulty of comprehending the original specification, the lack of any mechanical proof of the consistency of the specification and the difficulty of dealing with distribution and atomicity refinement. In this paper we elucidate how a new formal notation and tool can help to overcome these difficulties

The Paris Residential Market: Driving Factors and Market Behaviour 1973-2001

In this paper we investigate the driving factors associated with the Paris apartment market. We explore a database of nearly 230 000 transactions for residential properties in the Paris area over the 1973 – 2001 period. We develop a factorial model that may capture the systematic link between residential prices and a set of predefined economic variables or a linear combination of these economic variables. We assume that capital growth rates in real estate are related to the variables we defined in the last paragraph. We measure this link which underlines the ‘true path’ of the real estate market: in that way we can develop an index as a function of many other indices. The methodology we develop, based on a multifactor approach to apartment price movements in the long run, has two main advantages over traditional indices. Firstly, we are able to identify the main driving factors for the Paris residential market. And secondly, the factors thus derived can be used to generate a “factor model” useful in comparison to existing capital growth indices and that provides valuable intuition for forecasting residential prices.Real estate indexes; Repeat sales; Risk factors

Ionization state, excited populations and emission of impurities in dynamic finite density plasmas: I. The generalized collisional-radiative model for light elements

The paper presents an integrated view of the population structure and its role in establishing the ionization state of light elements in dynamic, finite density, laboratory and astrophysical plasmas. There are four main issues, the generalized collisional-radiative picture for metastables in dynamic plasmas with Maxwellian free electrons and its particularizing to light elements, the methods of bundling and projection for manipulating the population equations, the systematic production/use of state selective fundamental collision data in the metastable resolved picture to all levels for collisonal-radiative modelling and the delivery of appropriate derived coefficients for experiment analysis. The ions of carbon, oxygen and neon are used in illustration. The practical implementation of the methods described here is part of the ADAS Project

Petrodollars and imports of oil exporting countries

This paper investigates the empirical determinants of import demand in oil exporting countries. Using a new dataset including a large cross section of oil exporting countries, we show with a panel cointegration analysis that import demand in these countries depends positively on domestic demand and exports, the real exchange rate and the price of oil. Fiscal surpluses, on the other hand, tend to reduce the demand for imports. More specifically, our import elasticities estimated for oil exporting countries are not far from estimates found in the literature on industrial countries. In particular, we conclude that the import elasticity with respect to domestic activity is larger than one – a finding which is in contrast to standard theoretical predictions but in line with most empirical findings for other countries. These results are robust over a wide set of alternative specifications. JEL Classification: F14, F01, Q43Import Equation, oil exporting countries, Panel Cointegration

Do entry barriers, perceived by SMEs, affect real antry? Some evidence from the Netherlands

The objective of this paper is to analyse the relationship between perceived entry barriers and real entry. Real entry rates are interpreted as an indicator for the dynamics in an industry. The major hypothesis of this paper is that important entry barriers restrict new entry. Real entry rates are provided by a starter ratio for different industrial sectors and provinces in the Netherlands.

The composition of Event-B models

The transition from classical B [2] to the Event-B language and method [3] has seen the removal of some forms of model structuring and composition, with the intention of reinventing them in future. This work contributes to thatreinvention. Inspired by a proposed method for state-based decomposition and refinement [5] of an Event-B model, we propose a familiar parallel event composition (over disjoint state variable lists), and the less familiar event fusion (over intersecting state variable lists). A brief motivation is provided for these and other forms of composition of models, in terms of feature-based modelling. We show that model consistency is preserved under such compositions. More significantly we show that model composition preserves refinement