4 research outputs found
A Calculus of Mobile Resources
We introduce a calculus of Mobile Resources (MR) tailored for the design and analysis of systems containing mobile, possibly nested, computing devices that may have resource and access constraints, and which are not copyable nor modifiable per se. We provide a reduction as well as a labelled transition semantics and prove a correspondence be- tween barbed bisimulation congruence and a higher-order bisimulation. We provide examples of the expressiveness of the calculus, and apply the theory to prove one of its characteristic properties
Validating a Web Service Security Abstraction by Typing
An XML web service is, to a first approximation, an RPC service in which
requests and responses are encoded in XML as SOAP envelopes, and transported
over HTTP. We consider the problem of authenticating requests and responses at
the SOAP-level, rather than relying on transport-level security. We propose a
security abstraction, inspired by earlier work on secure RPC, in which the
methods exported by a web service are annotated with one of three security
levels: none, authenticated, or both authenticated and encrypted. We model our
abstraction as an object calculus with primitives for defining and calling web
services. We describe the semantics of our object calculus by translating to a
lower-level language with primitives for message passing and cryptography. To
validate our semantics, we embed correspondence assertions that specify the
correct authentication of requests and responses. By appeal to the type theory
for cryptographic protocols of Gordon and Jeffrey's Cryptyc, we verify the
correspondence assertions simply by typing. Finally, we describe an
implementation of our semantics via custom SOAP headers.Comment: 44 pages. A preliminary version appears in the Proceedings of the
Workshop on XML Security 2002, pp. 18-29, November 200
Synthesising Labelled Transitions and Operational Congruences in Reactive Systems, Part 1
The dynamics of process calculi, e.g. CCS, have often been defined using a labelled transition system (LTS). More recently it has become common when defining dynamics to use reaction rules ---i.e. unlabelled transition rules--- together with a structural congruence. This form, which I call a reactive system, is highly expressive but is limited in an important way: LTSs lead more naturally to operational equivalences and preorders. This paper shows how to synthesise an LTS for a wide range of reactive systems. A label for an agent (process) `a' is defined to be any context `F' which intuitively is just large enough so that the agent `Fa' (`a' in context `F') is able to perform a reaction step. The key contribution of my work is the precise definition of ``just large enough'' in terms of the categorical notion of relative pushout (RPO). I then prove that several operational equivalences and preorders (strong bisimulation, weak bisimulation, the traces preorder, and the failures preorder) are congruences when sufficient RPOs exist