219 research outputs found
Multiparty session actors
Actor coordination armoured with a suitable protocol description language has been
a pressing problem in the actors community. We study the applicability of multiparty session type
(MPST) protocols for verification of actor programs. We incorporate sessions to actors by introducing
minimum additions to the model such as the notion of actor roles and protocol mailboxes. The
framework uses Scribble, which is a protocol description language based on multiparty session types.
Our programming model supports actor-like syntax and runtime verification mechanism guaranteeing
communication safety of the participating entities. An actor can implement multiple roles in a
similar way as an object can implement multiple interfaces. Multiple roles allow for cooperative
inter-concurrency in a single actor. We demonstrate our framework by designing and implementing a
session actor library in Python and its runtime verification mechanism. Benchmark results demonstrate
that the runtime checks induce negligible overhead. We evaluate the applicability of our verification
framework to specify actor interactions by implementing twelve examples from an actor benchmark
suit
Contract representation for validation and run time monitoring
PhD ThesisOrganisations are increasingly using the Internet to offer their own services and to utilise the
services of others. This naturally leads to resource sharing across organisational boundaries.
Nevertheless, organisations will require their interactions with other organisations to be
strictly controlled. In the paper-based world, business interactions, information exchange and
sharing have been conducted under the control of contracts that the organisations sign. The
world of electronic business needs to emulate electronic equivalents of the contract based
business management practices.
This thesis examines how a 'conventional' contract can be converted into its
electronic equivalent and how it can be used for controlling business interactions taking place
through computer messages. To implement a contract electronically, a conventional text
contract needs to be described in a mathematically precise notation so that the description can
be subjected to rigorous analysis and freed from the ambiguities that the original humanoriented
text is likely to contain. Furthermore, a suitable run time infrastructure is required for
monitoring the executable version of the contract.
To address these issues, this thesis describes how standard conventional contracts can
be converted into Finite State Machines (FSMs). It is illustrated how to map the rights and
obligations extracted from the clauses of the contract into the states, transition and output
functions, and input and output symbols of a FSM.
The thesis then goes on to develop a list of correctness properties that a typical
executable business contract should satisfy. A contract model should be validated against
safety properties, which specify situations that the contract must not get into (such as
deadlocks, unreachable states .... etc), and liveness properties, which detail qualities that
would be desirable for the contract to contain (responsiveness, accessibility .... etc). The FSM
description can then be subjected to model checking. This is demonstrated with the aid of
examples using the Promela language and the Spin validator.
Subsequently, the FSM representation can be used to ensure that the clauses
stipulated in the contract are observed when the contract is executed. The requirements of a
suitable run time infrastructure for monitoring contract compliance are discussed and a
prototype middleware implementation is presented.UK Engineering and Physical Sciences Research
Council (EPSRC)
Terrain Representation And Reasoning In Computer Generated Forces : A Survey Of Computer Generated Forces Systems And How They Represent And Reason About Terrain
Report on a survey of computer systems used to produce realistic or intelligent behavior by autonomous entities in simulation systems. In particular, it is concerned with the data structures used by computer generated forces systems to represent terrain and the algorithmic approaches used by those systems to reason about terrain
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