170,393 research outputs found
Representation Theorems for Petri Nets
No full textThis paper retraces, collects, summarises, and mildly extends the contributions of the authors --- both together and individually --- on the theme of representing the space of computations of Petri nets in its mathematical essence
On the Algebraic Structure of Petri Nets
No full textThis paper retraces, collects, and summarises the contributions of the author --- both individually and in collaboration with others --- on the theme of algebraic, compositional approaches to the semantics of Petri nets
Transition Systems with Independence and Multi-Arcs
No full textWe extend the model of transition systems with independence in order to provide it with a feature relevant in the noninterleaving analysis of concurrent systems, namely multi-arcs. Moreover, we study the relationships between the category of transition systems with independence and multi-arcs and the category of labeled asynchronous transition systems, extending the results recently obtained by the authors for (simple) transition systems with independence (cf. Proc. CONCUR'96), and yielding a precise characterisation of transition systems with independence and multi-arcs in terms of (event-maximal, diamond-extensional) labeled asynchronous transition systems
Role-based access control for a distributed calculus
No full textRole-based access control (RBAC) is increasingly attracting attention because it reduces the complexity and cost of security administration by interposing the notion of role in the assignment of permissions to users. In this paper, we present a formal framework relying on an extension of the -calculus to study the behaviour of concurrent systems in a RBAC scenario. We define a type system ensuring that the specified policy is respected during computations, and a behavioural equivalence to equate systems. We then consider a more sophisticated feature that can be easily integrated in our framework, i.e., the possibility of automatically adding role activations and deactivations to processes to be run under a given policy (whenever possible). Finally, we show how the framework can be easily extended to express significant extensions of the core RBAC model, such as roles hierarchies or constraints determining the acceptability of the system components
Models of Computation: A Tribute to Ugo Montanari’s Vision
No full textUgo’s research activity in the area of Models of Computation (MoC, for short) has been prominent, influential and broadly scoped. In this introductory contribution we would like to recall some of the influential MoC models put forward by Ugo which cut across the three approaches
An Approach to the Category of Net Computations
No full textWe introduce the notion of strongly concatenable process as a refinement of concatenable processes [DMM89] which can be expressed axiomatically via a functor from the category of Petri nets to an appropriate category of symmetric strict monoidal categories, in the precise sense that, for each net , the strongly concatenable processes of are isomorphic to the arrows of . In addition, we identify a coreflection right adjoint to and characterize its replete image, thus yielding an axiomatization of the category of net computations
A Distributed Calculus for Role-Based Access Control
No full textRole-based access control (RBAC) is increasingly attracting attention because it reduces the complexity and cost of security administration by interposing the notion of role in the assignment of permissions to users. In this paper, we present a formal framework relying on an extension of the π calculus to study the behavior of concurrent systems in a RBAC scenario. We define a type system ensuring that the specified policy is respected during computations, and a bisimulation to equate systems. The theory is then applied to three meaningful examples, namely finding the ‘minimal’ policy to run a given system, refining a system to be run under a given policy (whenever possible), and minimizing the number of users in a given system without changing the overall behavior
The Inheritance Anomaly: Ten years after
No full textThe term inheritance anomaly was coined in 1993 by Matsuoka and Yonezawa [15] to refer to the problems arising by the coexistence of inheritance and concurrency in concurrent object oriented languages (COOLs). The quirks arising by such combination have been observed since the early eighties, when the first experimental COOLs were designed [3]. In the nineties COOLs turned from research topic to widely used tools in the everyday programming practice, see e.g. the Java [9] experience. This expository paper extends the survey presented in [15] to account for new and widely used COOLs, most notably Java and
A Dependently Typed Ambient Calculus
No full textThe Ambient calculus is a successful model of distributed, mobile computation, and has been the vehicle of new ideas for resource access control. Mobility types have been used to enforce elementary access control policies, expressed indirectly via classification of ambients in groups by means of ‘group types.’ The paper presents a theory of dependent types for the Ambient calculus which allows greater flexibility, while keeping the complexity away from the programmer into the type system
On the Category of Petri Net Computations
No full textWe introduce the notion of strongly concatenable process as a refinement of concatenable processes [DMM89] which can be expressed axiomatically via a functor from the category of Petri nets to an appropriate category of symmetric strict monoidal categories, in the precise sense that, for each net , the strongly concatenable processes of are isomorphic to the arrows of . In addition, we identify a coreflection right adjoint to and characterize its replete image, thus yielding an axiomatization of the category of net computations
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