A compositional Semantics for CHR

Constraint Handling Rules (CHR) are a committed-choice declarative language which has been designed for writing constraint solvers. A CHR program consists of multi-headed guarded rules which allow one to rewrite constraints into simpler ones until a solved form is reached. CHR has received a considerable attention, both from the practical and from the theoretical side. Nevertheless, due the use of multi-headed clauses, there are several aspects of the CHR semantics which have not been clarified yet. In particular, no compositional semantics for CHR has been defined so far. In this paper we introduce a fix-point semantics which characterizes the input/output behavior of a CHR program and which is and-compositional, that is, which allows to retrieve the semantics of a conjunctive query from the semantics of its components. Such a semantics can be used as a basis to define incremental and modular analysis and verification tools

Heterodox Central Banking

This paper discusses theoretical and practical aspects of the various unconventional central bank policies during the 2008-2009 crisis. In terms of theory, we first discuss the role of credibility in the attainment of inflationary goals once the nominal interest rate is at a lower bound, paying particular attention to the role of the central bank’s balance sheet. Additionally, we present a model which has at its core a financial imperfection that highlights the role of bank’s capital as well as the relevance of alternative credit policies that can be used to deal with financial distress. On the other hand, we review evidence regarding the recent experience. We discuss the timing and type of observed unconventional policies. We then explore alternative measures to assess the stance of monetary policy in a situation when the policy rate has reached its lower bound. Finally, we present some descriptive evidence on the effect of the applied policies on the shape of the yield curve and the lending-deposit spread.

Contract-theoretic approaches to wages and displacement

Wages