System of spheres-based multiple contractions

We propose a new class of multiple contraction operations — the system of spheres-based multiple contractions — which are a generalization of Grove’s system of spheres-based (singleton) contractions to the case of contractions by (possibly non-singleton) sets of sentences. Furthermore, we show that this new class of functions is a subclass of the class of the partial meet multiple contractions.info:eu-repo/semantics/publishedVersio

Possible worlds semantics for partial meet multiple contraction

In the logic of theory change, the standard model is AGM, proposed by Alchourrón et al. (J Symb Log 50:510–530, 1985). This paper focuses on the extension of AGM that accounts for contractions of a theory by a set of sentences instead of only by a single sentence. Hansson (Theoria 55:114–132, 1989), Fuhrmann and Hansson (J Logic Lang Inf 3:39–74, 1994) generalized Partial Meet Contraction to the case of contractions by (possibly non-singleton) sets of sentences. In this paper we present the possible worlds semantics for partial meet multiple contractions.info:eu-repo/semantics/publishedVersio

IMPOSTO SOBRE TRABALHO E SEU IMPACTO NOS MERCADOS DE TRABALHO FORMAL E INFORMAL

This paper aims to analyze the effects of payroll taxes on the determination of the degree of informality and the main indicators of the Brazilian labor market, considering both aggregate and disaggregate indicators by qualification level. For that purpose, a two- sector model is developed, where firms of both sectors use qualified and non-qualified workers as inputs for production. The demand for labor is determined by workers' productivity while the supply side is represented by wage curves, which are specific to each sector and qualification group. The results show that reducing payroll taxes has a significant effect over the formality degree and increases both employment level and earnings.

Credibility-limited base revision: new classes and their characterizations

In this paper we study a kind of operator —known as credibility-limited base revisions— which addresses two of the main issues that have been pointed out to the AGM model of belief change. Indeed, on the one hand, these operators are defined on belief bases (rather than belief sets) and, on the other hand, they are constructed with the underlying idea that not all new information is accepted. We propose twenty different classes of credibility limited base revision operators and obtain axiomatic characterizations for each of them. Additionally we thoroughly investigate the interrelations (in the sense of inclusion) among all those classes. More precisely, we analyse whether each one of those classes is or is not (strictly) contained in each of the remaining ones.info:eu-repo/semantics/publishedVersio