Bigraphical Location Models

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Type Systems for Bigraphs

We propose a novel and uniform approach to type systems for (process) calculi, which roughly pushes the challenge of designing type systems and proving properties about them to the meta-model of bigraphs. Concretely, we propose to define type systems for the term language for bigraphs, which is based on a fixed set of elementary bigraphs and operators on these. An essential elementary bigraph is an ion, to which a control can be attached modelling its kind (its ordered number of channels and whether it is a guard), e.g. an input prefix of pi-calculus. A model of a calculus is then a set of controls and a set of reaction rules, collectively a bigraphical reactive system (BRS). Possible advantages of developing bigraphical type systems include: A deeper understanding of a type system itself and its properties; transfer of the type systems to the concrete family of calculi that the BRS models; and the possibility of modularly adapting the type systems to extensions of the BRS (with new controls). As proof of concept we present a model of a pi-calculus, develop an i/o-type system with subtyping on this model, prove crucial properties (including subject reduction) for this type system, and transfer these properties to the (typed) pi-calculus

E.: Compositional specification of commercial contracts. M.S. term project

Abstract. We present a declarative language for compositional specification of contracts governing the exchange of resources. It extends Eber and Peyton Jones’s declarative language for specifying financial contracts [JE03] to the exchange of money, goods and services amongst multiple parties, and it complements McCarthy’s Resources, Events and Agents (REA) accounting model [McC82] with a view-independent formal contract model that supports definition of user-defined contracts, automatic monitoring under execution, and user-definable analysis of their state before, during and after execution. We provide several realistic examples of commercial contracts and their analyses. A variety of (real) contracts can be expressed in such a fashion as to support their integration, management and analysis in an operational environment that registers events. The language design is driven by both domain considerations and semantic language design methods: A contract denotes a set of traces of events, each of which is an alternative way of concluding the contract successfully, which gives rise to a CSP-style [BHR84,Hoa85] denotational semantics. The denotational semantics drives the development of a sound and complete small-step operational semantics, where a partially executed contract is represented as a (full) contract that represents the remaining contractual commitments. This operational semantics is then systematically refined in two stages to an instrumented operational semantics that reflects the bookkeeping practice of identifying the specific contractual commitment a particular event matches at the time the event occurs, as opposed to delaying this matching until the contract is concluded.

Int J Softw Tools Technol Transfer DOI 10.1007/s10009-006-0010-1 SPECIAL SECTION ON LEVERAGING APPLICATIONS OF FORMAL METHODS Compositional specification of commercial contracts

Abstract We present a declarative language for compositional specification of contracts governing the exchange of resources. It extends Eber and Peyton Jones’s declarative language for specifying financial contracts (Jones et al. in The Fun of Programming. 2003) to the exchange of money, goods and services amongst multiple parties and complements McCarthy’s Resources, Events and Agents (REA) accounting model (McCarthy in Account Rev. LVII(3), 554–578, 1982) with a viewindependent formal contract model that supports definition of user-defined contracts, automatic monitoring under execution and user-definable analysis of their state before, during and after execution. We provide several realistic examples of commercial contracts and their analyses. A variety of (real) contracts can be expressed in such a fashion as to support their integration, management and analysis in an operational environment tha