2,721 research outputs found
Rational Term Rewriting
No full textRational terms (possibly infinite terms with finitely many subterms) can be represented in a finite way via mu-terms, that is, terms over a signature extended with self-instantiation operators. For example, f(omega) = f(f(f(...))) can be represented as mu(x).f(x) (or also as mu(x).f(f(x)), f(mu x.f(x)),...). Now, if we reduce a mu-term t to s via a rewriting rule using standard notions of the theory of Term Rewriting Systems, how are the rational terms corresponding to t and to s related? We answer to this question in a satisfactory way, resorting to the definition of infinite parallel rewriting proposed by Corradini. We also provide a simple, algebraic description of mu-term rewriting through a variation of Meseguer's Rewriting Logic formalism
F. Corradini. A step forward towards equational ax- iomatizations of Milner bisimulation in Kleene star
No full textOn Testing Urgency through Laziness over Processes with Durational Actions
No full textAbstractIn this paper we study restrictions on the expressivity of the timed process algebra with durational actions which allow to test urgency of actions through actions which can be delayed arbitrarily long before firing. This solves a conjecture in Corradini (Inform. and Comput. 145 (1998) 191–230)
Investigating Reddit to detect subreddit and author stereotypes and to evaluate author assortativity
No full textIn recent years, Reddit has attracted the interest of many researchers due to its popularity all over the world. In this article, we aim at providing a contribution to the knowledge of this social network by investigating three of its aspects, interesting from the scientific viewpoint, and, at the same time, by analysing a large number of applications. In particular, we first propose a definition and an analysis of several stereotypes of both subreddits and authors. This analysis is coupled with the definition of three possible orthogonal taxonomies that help us to classify stereotypes in an appropriate way. Then, we investigate the possible existence of author assortativity in this social medium; specifically, we focus on co-posters, that is, authors who submitted posts on the same subreddit
Modelling and analyzing adaptive self-assembling strategies with Maude
No full textBuilding adaptive systems with predictable emergent behavior is a challenging task and it is becoming a critical need. The research community has accepted the challenge by introducing approaches of various nature: from software architectures, to programming paradigms, to analysis techniques. We recently proposed a conceptual framework for adaptation centered around the role of control data. In this paper we show that it can be naturally realized in a reflective logical language like Maude by using the Reflective Russian Dolls model. Moreover, we exploit this model to specify and analyse a prominent example of adaptive system: robot swarms equipped with obstacle-avoidance self-assembly strategies. The analysis exploits the statistical model checker PVesta
Performance Preorder and Competitive Equivalence
No full textA preorder based on execution speed, called performance preorder, is introduced for a simple process algebra with durational actions. Two processes E and F are related -E (Square image of or equal to)p F-if they have the same functionality (in this case, we have chosen strong bisimulation equivalence) and E is at least as fast as F. Hence, this preorder supports the stepwise refinement "from specification to implementation" by increasing efficiency while retaining the same functionality. We show that the problem of finding faster implementations for a specification is connected to the problem of finding more distributed implementations of the same specification. Both performance preorder and the induced equivalence, called competitive equivalence, are provided with sound and complete axiomatizations for finite agents
An extra-regional collaborative approach to Smart Specialization
No full textThis chapter outlines reasons for supporting and developing extra-regional collaboration between lagging and leading regions. It highlights the difficulties and inherent risks that typically lie within such an approach. We then consider existing European Union (EU) mechanisms to foster such collaboration, and explore these in the context of some illustrative examples from case research in Cornwall, UK, and Puglia, Italy. Both are officially recognised as lagging EU regions, and have been in receipt of significant EU funding. We conclude with some suggestions for policy
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