1,721,409 research outputs found
On-line Commerce and Town Centre Retailers' Experience
No full textThis paper is an attempt to develop a new way to sell products or services for retailers within town centres. An analysis of the literature revealed that the use of the Internet and digital commerce strategies are rarely used as tools to revitalize urban retail and develop a multidimensional experience of place. Thus, this paper aims to highlight which new modes of online commerce—e-commerce, s-commerce and m-commerce—are more suitable than others to help town centre retailers revitalize the place where they work. The research questions are as follows: 1) What are the origins of the growth and development of new forms of selling? and 2) How might town centre retailers integrate new forms of selling with traditional retailing? In answering the previously stated questions, this paper provides a proposed model that, by combining physical and virtual means to sell products and services, can provide specific strengths in revitalizing town centres
Petri Inheritance: The Foundation of Nondeterministic, Concurrent Systems
Get PDFThe personal contacts of the first author with Carl Adam Petri and Petri nets are initially described and the role of Petri nets as a connector algebra is then examined
Semantic foundations for generalized rewrite theories
No full textSince its introduction, more than one decade ago, rewriting logic has attracted the interest of both theorists and practitioners, who have contributed in showing its generality as a semantic and logical framework and also as a programming paradigm. The experimentation conducted in these years has suggested that some significant extensions to the original definition of the logic would be very useful in practice. In particular, the Maude system now supports subsorting and conditional sentences in the equational logic for data, and also frozen arguments to block undesired nested rewrites; moreover, it allows equality and membership assertions in rule conditions. In this paper, we give a detailed presentation of the inference rules, model theory, and completeness of such generalized rewrite theories
Some algebraic laws for spans
No full textThis paper investigates some key algebraic properties of the categories of spans and cospans (up to isomorphic supports) over the category Set of (small) sets and functions, analyzing the monoidal structures induced over both spans and cospans by cartesian product and disjoint union of sets. Our results find analogous counterparts in (and are partly inspired by) the theory of relational algebras, thus our paper also sheds some light on the relationship between (co)spans and the categories of (multi)relations and of equivalence relations. And, since (co)spans yield an intuitive presentation of dynamical systems with input and output interfaces, our results introduce an expressive, two-fold algebra that can serve as a specification formalism for rewriting systems and for composing software modules
Local Completeness for Program Correctness and Incorrectness (Invited Talk)
No full textProgram correctness techniques aim to prove the absence of bugs, but can yield false alarms because they tend to over-approximate program semantics. Vice versa, program incorrectness methods are aimed to detect true bugs, without false alarms, but cannot be used to prove correctness, because they under-approximate program semantics. In this invited talk we will overview our ongoing research on the use of the abstract interpretation framework to combine under- and over-approximation in the same analysis and distill a logic for program correctness and incorrectness
Calculi for Service Oriented Computing
No full textIt is widely recognised that process calculi stay to concurrent computing as lambda-calculus stays to sequential computing; in fact, they lay abstract, rigorous foundations for the analysis of interactive, communicating systems. Nowadays, the increasing popularity of Service-Oriented Computing (SOC) challenges the quest for novel abstractions tailored to the well-disciplined handling of specific issues, like long running interactions, orchestration, and unexpected events. In fact, these features emerge neatly in most SOC applications and need to be studied as first-class aspects, whereas they would be obfuscated if dealt with by sophisticated encoding in traditional process calculi. This paper overviews some of the most recent proposals emerged in the literature, pointing out their main characteristics and presents in more detail one such proposal, called caspis, by providing several examples to give evidence of its flexibility. No prior acquaintance with process calculi is assumed, indeed a gentle introduction to their basics is provided before the more advanced material be presented
Tile Logic for Synchronized Rewriting of Concurrent Systems
No full textTile logic is a framework to reason about the dynamic evolution of concurrent systems in a modular way. It extends rewriting logic (in the unconditional case) by adding rewriting synchronization and side effects. This dissertation concerns both theoretical and implementative issues of tile models of computation where the mathematical structures representing configurations (i.e., system states) and observations (i.e., observable actions) rely on the same common auxiliary structure (e.g., for tupling, projecting, etc.). We proceed by considering maybe the simplest tile model (whose configurations and observations are just commutative monoids, and their sequential and parallel compositions coincide) and showing that it yields an original net model, called zero safe net, which comes equipped with a primitive notion of transition synchronization, which is missing in ordinary Petri nets. The operational and abstract semantics of the model are expressed in the language of Net Theory and also..
Types and deadlock freedom in a calculus of services, sessions and pipelines
No full textThe notion of a session is fundamental in service-oriented applications, as it serves to separate interactions between clients and different instances of the same service, and to group together logical units of work. Recently, the Service Centered Calculus (SCC) has been proposed as a process calculus designed around the concept of a dyadic session between a service side and an invoker side, where interaction protocols and service orchestration can be conveniently expressed. In this paper we propose a generic type system to collect services' behaviours and then we fix a class of well-typed processes that are guaranteed to be deadlock free, in the sense that they either diverge by invoking new service instances or reach a normal form. The type system is based on previous research on traditional mobile calculi, here conveniently extended and simplified thanks to the neat discipline imposed by the linguistic primitives of SCC
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