11 research outputs found
Lightening Global Types
Global session types prevent participants from waiting for never coming
messages. Some interactions take place just for the purpose of informing
receivers that some message will never arrive or the session is terminated. By
decomposing a big global type into several light global types, one can avoid
such kind of redundant interactions. Lightening global types gives us cleaner
global types, which keep all necessary communications. This work proposes a
framework which allows to easily decompose global types into light global
types, preserving the interaction sequences of the original ones but for
redundant interactions.Comment: In Proceedings PLACES 2014, arXiv:1406.331
Comparing the expressive power of the Synchronous and the Asynchronous pi-calculus
The Asynchronous pi-calculus, as recently proposed by Boudol and,
independently, by Honda and Tokoro, is a subset of the pi-calculus which
contains no explicit operators for choice and output-prefixing. The
communication mechanism of this calculus, however, is powerful enough to
simulate output-prefixing, as shown by Boudol, and input-guarded choice, as
shown recently by Nestmann and Pierce. A natural question arises, then, whether
or not it is possible to embed in it the full pi-calculus. We show that this is
not possible, i.e. there does not exist any uniform, parallel-preserving,
translation from the pi-calculus into the asynchronous pi-calculus, up to any
``reasonable'' notion of equivalence. This result is based on the incapablity
of the asynchronous pi-calculus of breaking certain symmetries possibly present
in the initial communication graph. By similar arguments, we prove a separation
result between the pi-calculus and CCS.Comment: 10 pages. Proc. of the POPL'97 symposiu
Design of asynchronous supervisors
One of the main drawbacks while implementing the interaction between a plant
and a supervisor, synthesised by the supervisory control theory of
\citeauthor{RW:1987}, is the inexact synchronisation. \citeauthor{balemiphdt}
was the first to consider this problem, and the solutions given in his PhD
thesis were in the domain of automata theory. Our goal is to address the issue
of inexact synchronisation in a process algebra setting, because we get
concepts like modularity and abstraction for free, which are useful to further
analyze the synthesised system. In this paper, we propose four methods to check
a closed loop system in an asynchronous setting such that it is branching
bisimilar to the modified (asynchronous) closed loop system. We modify a given
closed loop system by introducing buffers either in the plant models, the
supervisor models, or the output channels of both supervisor and plant models,
or in the input channels of both supervisor and plant models. A notion of
desynchronisable closed loop system is introduced, which is a class of
synchronous closed loop systems such that they are branching bisimilar to their
corresponding asynchronous versions. Finally we study different case studies in
an asynchronous setting and then try to summarise the observations (or
conditions) which will be helpful in order to formulate a theory of
desynchronisable closed loop systems
A logical interface description language for components
Motivated by our earlier work on the IWIM model and the Manifold language, in this paper, we attend to some of the basic issues in component-based software. We present a formal model for such systems, a formal-logic-based component interface description language that conveys the observable semantics of components, a formal system for deriving the semantics of a composite system out of the semantics of its constituent components, and the conditions under which this derivation system is sound and complete. Our main results in this paper are the theorems that formulate the notion of compositionality and the completeness of the derivation system that supports this property in a component-based system
Saturating automata for game semantics
Saturation is a fundamental game-semantic property satisfied by strategies
that interpret higher-order concurrent programs. It states that the strategy
must be closed under certain rearrangements of moves, and corresponds to the
intuition that program moves (P-moves) may depend only on moves made by the
environment (O-moves).
We propose an automata model over an infinite alphabet, called saturating
automata, for which all accepted languages are guaranteed to satisfy a closure
property mimicking saturation.
We show how to translate the finitary fragment of Idealized Concurrent Algol
(FICA) into saturating automata, confirming their suitability for modelling
higher-order concurrency. Moreover, we find that, for terms in normal form, the
resultant automaton has linearly many transitions and states with respect to
term size, and can be constructed in polynomial time. This is in contrast to
earlier attempts at finding automata-theoretic models of FICA, which did not
guarantee saturation and involved an exponential blow-up during translation,
even for normal forms.Comment: Presented at MFPS 202
Theories for Session-based Governance for Large-scale Distributed Systems
PhDLarge-scale distributed systems and distributed computing are the pillars
of IT infrastructure and society nowadays. Robust theoretical principles for
designing, building, managing and understanding the interactive behaviours
of such systems need to be explored. A promising approach for establishing
such principles is to view the session as the key unit for design, execution
and verification.
Governance is a general term for verifying whether activities meet the specified
requirements and for enforcing safe behaviours among processes. This
thesis, based on the asynchronous -calculus and the theory of session types,
provides a monitoring framework and a theory for validating specifications,
verifying mutual behaviours during runtime, and taking actions when noncompliant
behaviours are detected. We explore properties and principles
for governing large-scale distributed systems, in which autonomous and heterogeneous
system components interact with each other in the network to
accomplish application goals.
This thesis, incorporating lessons from my participation in a substantial
practical project, the Ocean Observatories Initiative (OOI), proposes an
asynchronous monitoring framework and the process calculus for dynamically
governing the asynchronous interactions among distributed multiple
applications. We prove that this monitoring model guarantees the satisfaction
of global assertions, and state and prove theorems of local and global
safety, transparency, and session fidelity. We also study and introduce the
semantic mechanisms for runtime session-based governance and the principles
of validation of stateful specifications through capturing the runtime
asynchronous interactions.EPSRC grants EP/G015481/1; Queen Mary University of Londo