3,210 research outputs found

    "Organic District": identification methodology and agricultural policy objectives

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    Italy, unlike other countries, has included the territorial dimension in the recent interventions and regulations of organic agriculture, introducing explicitly the concept of “organic district”. It is defined as a local productive system with a high agricultural vocation where organic production and processing practices are predominant. The main object of this new subject is to promote the diffusion of organic agriculture focusing on the productive and environmental territorial characteristic. In this poster, after a general definition of the organic districts, as they are introduced in the Italian regulations, a method for their identification in a region is proposed. In the final part, some considerations about the role of the organic district within the general framework of agro-environmental policies are developed.organic district, agro-environmental policies, organic agriculture, Agricultural and Food Policy, Environmental Economics and Policy,

    Bigraphical models for protein and membrane interactions

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    We present a bigraphical framework suited for modeling biological systems both at protein level and at membrane level. We characterize formally bigraphs corresponding to biologically meaningful systems, and bigraphic rewriting rules representing biologically admissible interactions. At the protein level, these bigraphic reactive systems correspond exactly to systems of kappa-calculus. Membrane-level interactions are represented by just two general rules, whose application can be triggered by protein-level interactions in a well-de\"ined and precise way. This framework can be used to compare and merge models at different abstraction levels; in particular, higher-level (e.g. mobility) activities can be given a formal biological justification in terms of low-level (i.e., protein) interactions. As examples, we formalize in our framework the vesiculation and the phagocytosis processes

    A framework for protein and membrane interactions

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    We introduce the BioBeta Framework, a meta-model for both protein-level and membrane-level interactions of living cells. This formalism aims to provide a formal setting where to encode, compare and merge models at different abstraction levels; in particular, higher-level (e.g. membrane) activities can be given a formal biological justification in terms of low-level (i.e., protein) interactions. A BioBeta specification provides a protein signature together a set of protein reactions, in the spirit of the kappa-calculus. Moreover, the specification describes when a protein configuration triggers one of the only two membrane interaction allowed, that is "pinch" and "fuse". In this paper we define the syntax and semantics of BioBeta, analyse its properties, give it an interpretation as biobigraphical reactive systems, and discuss its expressivity by comparing with kappa-calculus and modelling significant examples. Notably, BioBeta has been designed after a bigraphical metamodel for the same purposes. Hence, each instance of the calculus corresponds to a bigraphical reactive system, and vice versa (almost). Therefore, we can inherith the rich theory of bigraphs, such as the automatic construction of labelled transition systems and behavioural congruences

    An Algebra for Directed Bigraphs

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    We study the algebraic structure of directed bigraphs, a bigraphical model of computations with locations, connections and resources previously introduced as a unifying generalization of other variants of bigraphs. We give a sound and complete axiomatization of the (pre)category of directed bigraphs. Using this axiomatization, we give an adequate encoding of the Fusion calculus, showing the utility of the added directnes

    Controlling resource access in Directed Bigraphs

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    We study directed bigraph with negative ports, a bigraphical framework for representing models for distributed, concurrent and ubiquitous computing. With respect to previous versions, we add the possibility that components may govern the access to resources, like (web) servers control requests from clients. This framework encompasses many common computational aspects, such as name or channel creation, references, client/server connections, localities, etc, still allowing to derive systematically labelled transition systems whose bisimilarities are congruences. As application examples, we analyse the encodings of client/server communications through firewalls, of (compositional) Petri nets and of chemical reactions

    Fuzzy Algebraic Theories

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    In this work we propose a formal system for fuzzy algebraic reasoning. The sequent calculus we define is based on two kinds of propositions, capturing equality and existence of terms as members of a fuzzy set. We provide a sound semantics for this calculus and show that there is a notion of free model for any theory in this system, allowing us (with some restrictions) to recover models as Eilenberg-Moore algebras for some monad. We will also prove a completeness result: a formula is derivable from a given theory if and only if it is satisfied by all models of the theory. Finally, leveraging results by Milius and Urbat, we give HSP-like characterizations of subcategories of algebras which are categories of models of particular kinds of theories

    Closure Hyperdoctrines

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    (Pre)closure spaces are a generalization of topological spaces covering also the notion of neighbourhood in discrete structures, widely used to model and reason about spatial aspects of distributed systems. In this paper we present an abstract theoretical framework for the systematic investigation of the logical aspects of closure spaces. To this end, we introduce the notion of closure (hyper)doctrines, i.e. doctrines endowed with inflationary operators (and subject to suitable conditions). The generality and effectiveness of this concept is witnessed by many examples arising naturally from topological spaces, fuzzy sets, algebraic structures, coalgebras, and covering at once also known cases such as Kripke frames and probabilistic frames (i.e., Markov chains). By leveraging general categorical constructions, we provide axiomatisations and sound and complete semantics for various fragments of logics for closure operators. Hence, closure hyperdoctrines are useful both for refining and improving the theory of existing spatial logics, and for the definition of new spatial logics for new applications

    Deriving Barbed Bisimulations for Bigraphical Reactive Systems

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    We study the definition of a general abstract notion of barbed bisimilarity for reactive systems on bigraphs. More precisely, given a bigraphical reactive system, we define the corresponding barbs from the contextual labels given by the IPO construction, in a general and systematic way. These barbs correspond to observe which names on the interface are actually involved in reactions (and how). As examples, we apply this construction to the (bigraphical representation of the) pi-calculus and of Mobile Ambients, and compare the resulting barbed equivalences with those previously known for these calculi

    On The Axioms Of M,N\mathcal{M},\mathcal{N}-Adhesive Categories

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    Adhesive and quasiadhesive categories provide a general framework for the study of algebraic graph rewriting systems. In a quasiadhesive category any two regular subobjects have a join which is again a regular subobject. Vice versa, if regular monos are adhesive, then the existence of a regular join for any pair of regular subobjects entails quasiadhesivity. It is also known (quasi)adhesive categories can be embedded in a Grothendieck topos via a functor preserving pullbacks and pushouts along (regular) monomorphisms. In this paper we extend these results to M,N\mathcal{M}, \mathcal{N}-adhesive categories, a concept recently introduced to generalize the notion of (quasi)adhesivity. We introduce the notion of N\mathcal{N}-adhesive morphism, which allows us to express M,N\mathcal{M}, \mathcal{N}-adhesivity as a condition on the subobjects's posets. Moreover, N\mathcal{N}-adhesive morphisms allows us to show how an M,N\mathcal{M},\mathcal{N}-adhesive category can be embedded into a Grothendieck topos, preserving pullbacks and M,N\mathcal{M}, \mathcal{N}-pushouts
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