On the Expressivity and Applicability of Model Representation Formalisms

A number of first-order calculi employ an explicit model representation formalism for automated reasoning and for detecting satisfiability. Many of these formalisms can represent infinite Herbrand models. The first-order fragment of monadic, shallow, linear, Horn (MSLH) clauses, is such a formalism used in the approximation refinement calculus. Our first result is a finite model property for MSLH clause sets. Therefore, MSLH clause sets cannot represent models of clause sets with inherently infinite models. Through a translation to tree automata, we further show that this limitation also applies to the linear fragments of implicit generalizations, which is the formalism used in the model-evolution calculus, to atoms with disequality constraints, the formalisms used in the non-redundant clause learning calculus (NRCL), and to atoms with membership constraints, a formalism used for example in decision procedures for algebraic data types. Although these formalisms cannot represent models of clause sets with inherently infinite models, through an additional approximation step they can. This is our second main result. For clause sets including the definition of an equivalence relation with the help of an additional, novel approximation, called reflexive relation splitting, the approximation refinement calculus can automatically show satisfiability through the MSLH clause set formalism.Comment: 15 page

On the Expressivity and Applicability of Model Representation Formalisms

International audienceA number of first-order calculi employ an explicit model representation formalism in support of non-redundant inferences and for detecting satisfiability. Many of these formalisms can represent infinite Herbrand models. The first-order fragment of monadic, shallow, linear, Horn (MSLH) clauses, is such a formalism used in the approximation refinement calculus (AR). Our first result is a finite model property for MSLH clause sets. Therefore, MSLH clause sets cannot represent models of clause sets with inherently infinite models. Through a translation to tree automata, we further show that this limitation also applies to the linear fragments of implicit generalizations, which is the formalism used in the model-evolution calculus (ME), to atoms with disequality constraints, the formalisms used in the non-redundant clause learning calculus (NRCL), and to atoms with membership constraints, a formalism used for example in decision procedures for algebraic data types. Although these formalisms cannot represent models of clause sets with inherently infinite models, through an additional approximation step they can. This is our second main result. For clause sets including the definition of an equivalence relation with the help of an additional, novel approximation, called reflexive relation splitting, the approximation refinement calculus can automatically show satisfiability through the MSLH clause set formalism

From the "age of instability" to the "age of responsibility": economic uncertainty and sustainable investments

PurposeThis paper sets out to investigate investors' sustainable preferences under different market conditions. Specifically, the authors examine the existence of a positive sustainable asset pricing gap, and whether it is influenced by the socioeconomic and financial sentiments. The increase of uncertainty rises investors' skepticism whether sustainable companies are under-performing the traditional counterparts, causing larger increasing gap. Conversely, if sustainable assets are overperforming, the increase of market uncertainty raises investors' sustainable preferences.Design/methodology/approachThe authors examine the existence of a positive sustainable asset pricing gap, and whether it is influenced by the socioeconomic and financial sentiments. Through a quantile regression, the authors remark the variability of sustainable preferences where market participants, although recognizing the present and future value added of sustainable investing, also show skepticism (i.e. asymmetric tail behavior). However, the analysis of the total change of sustainable investments returns over time demonstrates the emergence of positive viewpoints incentivized by economic and market uncertainty.FindingsThe market-driven social responsibility exalts the positive insights regarding the future of sustainable developments. As the authors discuss along the paper, investors are gaining awareness about the environmental and social goals pursued by socially responsible companies. Hence, the authors consider how economic instability might stimulate the assessment of the social and environmental impact of the unsustainable production systems, switching investments toward virtuous sustainable companies. This could generate a series of positive externalities that might improve the welfare conditions of the whole society.Originality/valueThe authors conduct an original empirical exercise, combining different techniques (i.e. quantile regressions and wavelet analysis). To the best of the authors' knowledge, this is the first paper trying to evidence a systematic connection between market uncertainty and sustainable preferences accounting for different market states (thanks to quantile regressions)

Agents interaction and price dynamics: evidence from the laboratory

Using data collected from an experimental double auction market, we study the dynamics of interaction among traders. Our focus is on the effect the trading network has on price dynamics and price-fundamental convergence. At the aggregate level, the network of empirical exchanges reveals properties that are dissimilar from random graphs and, in particular, high centrality and high clustering. Precisely, these properties are identifiable as the cause of price volatility and divergence from the fundamental value. At the microscopic level, we find out how the topological properties of the network derive from the behavior of traders. In fact, our findings show that it is the unbridled trading action of very centralized players who implement a minority game, to give rise to volatility clustering and arbitrage opportunities

Unemployment and labor force participation in Italy

Purpose: Our main purpose is to test the unemployment invariance hypothesis in Italy. Design/methodology/approach: This paper provides an empirical investigation of the unemployment and labor force participation in Italy. Findings: Cointegration analysis results strongly suggest a clear long-run relationship between unemployment and labor force participation revealing a persistent and general added worker effect. Originality/value: Our results seem to confute the unemployment invariance hypothesis

Wasting energy or energizing waste? The public acceptance of waste-to-energy technology

Waste-to-energy (WtE) plants are pivotal for the circular economy and sustainable urban development. However, public acceptance is critical to their success, given widespread skepticism (often due to limited knowledge about the potential environmental and health risks). This work examines the public mindset, identifying factors that may explain the transition from opposition to strong support. It also explores how traditional technical analysis may be successfully integrated with social perspectives to improve policy effectiveness. To this end, an online survey was administered to a sample of 240 Italian consumers. Three groups are identified from survey data: (i) opponents, (ii) weak supporters, and (iii) strong supporters. Results show that perceived risk factors are central in explaining the difference between groups, with lower perceived health and environmental concerns associated with general support for the technology, and trust in local government management associated with strong (as compared to weak) support. Health, environmental, and safety/control concerns negatively affected willingness to pay. The main implications suggest that different perceptions exist for WtE given that they are a sustainable technology compared to landfill use but without compromising separate collection and more virtuous waste management practices. This social sustainable approach can be supported by policies that promote energizing waste

Bitcoin: Bubble that bursts or Gold that glitters?

This paper aims to shed light on the 2017 Bitcoin bubble. Firstly, by applying the dynamic time warping algorithm, we identify among several financial instruments a subsample of five assets with similar characteristics to the cryptocurrency bubble. Interestingly, among the fluctuations characterizing these assets, the algorithm shows a close affinity between the Bitcoin bubble and the 2000 NASDAQ Dotcom one. Once the subsample is identified, we study the (de)synchronization among these assets via the wavelet coherence approach. Although Bitcoin is poorly correlated with the other indices, given its scarce connection with the real economy, we observe switching phenomena among these instruments. A more careful study on these portfolio reallocations, conducted via an event study analysis, reveals that traders seem to redirect capital from stock markets and gold to Bitcoin in case of positive events of the cryptocurrency

Professional traders’ individual and social preferences under risk: Does group's wealth matter?

We studied whether professional traders’ risk attitudes varied according to social context. To this extent, we examined whether the level of wealth in the relevant group influenced traders’ risky decisions. The results showed that risk aversion decreased with increased income/wealth conditions in the group context