On the Reification of Global Constraints

We introduce a simple idea for deriving reified global constraints in a systematic way. It is based on the observation that most global constraints can be reformulated as a conjunction of pure functional dependency constraints together with a constraint that can be easily reified. We first show how the core constraints of the Global Constraint Catalogue can be reified and we then identify several reification categories that apply to at least 82% of the constraints in the Global Constraint Catalogue

Conjunctions of Among Constraints

Many existing global constraints can be encoded as a conjunction of among constraints. An among constraint holds if the number of the variables in its scope whose value belongs to a prespecified set, which we call its range, is within some given bounds. It is known that domain filtering algorithms can benefit from reasoning about the interaction of among constraints so that values can be filtered out taking into consideration several among constraints simultaneously. The present pa- per embarks into a systematic investigation on the circumstances under which it is possible to obtain efficient and complete domain filtering algorithms for conjunctions of among constraints. We start by observing that restrictions on both the scope and the range of the among constraints are necessary to obtain meaningful results. Then, we derive a domain flow-based filtering algorithm and present several applications. In particular, it is shown that the algorithm unifies and generalizes several previous existing results.Comment: 15 pages plus appendi

On Global Warming (Softening Global Constraints)

We describe soft versions of the global cardinality constraint and the regular constraint, with efficient filtering algorithms maintaining domain consistency. For both constraints, the softening is achieved by augmenting the underlying graph. The softened constraints can be used to extend the meta-constraint framework for over-constrained problems proposed by Petit, Regin and Bessiere.Comment: 15 pages, 7 figures. Accepted at the 6th International Workshop on Preferences and Soft Constraint

Time-Space Efficient Regression Testing for Configurable Systems

Configurable systems are those that can be adapted from a set of options. They are prevalent and testing them is important and challenging. Existing approaches for testing configurable systems are either unsound (i.e., they can miss fault-revealing configurations) or do not scale. This paper proposes EvoSPLat, a regression testing technique for configurable systems. EvoSPLat builds on our previously-developed technique, SPLat, which explores all dynamically reachable configurations from a test. EvoSPLat is tuned for two scenarios of use in regression testing: Regression Configuration Selection (RCS) and Regression Test Selection (RTS). EvoSPLat for RCS prunes configurations (not tests) that are not impacted by changes whereas EvoSPLat for RTS prunes tests (not configurations) which are not impacted by changes. Handling both scenarios in the context of evolution is important. Experimental results show that EvoSPLat is promising. We observed a substantial reduction in time (22%) and in the number of configurations (45%) for configurable Java programs. In a case study on a large real-world configurable system (GCC), EvoSPLat reduced 35% of the running time. Comparing EvoSPLat with sampling techniques, 2-wise was the most efficient technique, but it missed two bugs whereas EvoSPLat detected all bugs four times faster than 6-wise, on average.Comment: 14 page

Reducing Regional Disparities in China: An Evaluation of Alternative Policies

Regional disparities in output per capita and income in China are large and persistent. They have been the subject of considerable concern to policy-makers at the highest level for decades, yet little is known about the effectiveness of various alternative policies which may be used to combat them. In this paper we address this issue by analysing the effectiveness of a range of policies by both regional and central governments. We use a small model with various features of the Chinese economy: two regions (the interior and the coast), two industries (agriculture and manufacturing), inter-regional capital mobility, internal migration subject to the hukou system of household registration and some features of the Chinese tax and expenditure system. The model is calibrated to Chinese data and simulated to analyse the effects of a number of policies on a range of variables but focussing on per capita output disparities and welfare. We find that a policy reducing internal migration costs is effective in reducing the per capita output gap but does so at a substantial cost to the coast. Policies which improve agricultural productivity in the interior region are most likely to both reduce the gap and make both regions better off. Changes in government consumption expenditure, central government fiscal redistributions and tax cuts, on the other hand, are less effective and have their long-run effectiveness reduced by migration.regional disparities, China, numerical modelling, hukou

Hiding Lorentz Invariance Violation with MOND

Ho\v{r}ava gravity is a attempt to construct a renormalizable theory of gravity by breaking the Lorentz Invariance of the gravitational action at high energies. The underlying principle is that Lorentz Invariance is an approximate symmetry and its violation by gravitational phenomena is somehow hidden to present limits of observational precision. Here I point out that a simple modification of the low energy limit of Ho\v{r}ava gravity in its non-projectable form can effectively camouflage the presence of a preferred frame in regions where the Newtonian gravitational field gradient is higher than $cH_0$; this modification results in the phenomenology of MOND at lower accelerations.Comment: 5 pages, revised field equation, discussion added on potentials and dark energy, in press PR

Key characteristics of employment regulation in the Middle East and North Africa

This note provides a general background of the main features of labor regulation in the Middle East and North Africa (MENA) and benchmarks them against international best practices. The note compiles information on available labor laws and other legal acts concerning employment protection regulation. Within the broader scope of labor regulation, and in order to assure regional comparability, information collected focuses on key issues in the labor law associated with commencing or terminating employment and during the period of employment (including maternity benefits). The main sources the data are the World Bank doing business 2010 and International Labour Organisation (ILO) databank. This note is a tool to provide policymakers and international organizations with a regional diagnose of how labor regulation affects labor market outcomes in MENA and inform client governments about strategic approaches to employment creation through labor policy and reform. This activity comes as a response to regional priorities in the context of the Arab World Initiative (AWI). One of the six strategic themes of the AWI focuses explicitly on employment creation as a top priority. Part of the World Bank's mandate under the AWI is to inform client governments about strategic approaches to employment creation through labor policy and reform.Labor Markets,Labor Policies,Labor Standards,Work&Working Conditions,Labor Management and Relations