Date: Monday, 28 January 2008
Speaker: Farhad Arbab
Room and time: 5161.0267 (Bernoulliborg), 16.00
Title: Third-Party Coordination of Distributed Services
Different aspects of coordination in Service Oriented Computing (SoC) have been
considered as separate, complementary (if not competing) concerns, such as
choreography and orchestration. Work on proposals and standards to deal with
these concerns is still on-going; however, the results appear as ad-hoc
(albeit useful) collections of ideas and constructs that convey no systematic
conceptual model or formal theoretical foundation. We believe a coherent approach
to deal with various aspects of coordination must consider all coordination concerns
as an integrated whole, and as an issue inseparable from the context of composition
(of services). Reo offers precisely such a model.
Reo is an exogenous coordination language based on a calculus of channel composition.
In Reo, services are composed using complex coordinators, called connectors, that
in turn are compositionally built out of simpler ones.The simplest connectors in Reo
are a set of mobile channels with well-defined behavior supplied by users. Reo supports
third-party composition and coordination of services: each connector in Reo imposes
a specific coordination pattern on the I/O operations performed by the services that it
interconnects, without the knowledge of those services. Alternative formal semantics
for Reo exist, e.g., based on stream calculus and constraint automata. Channel
composition in Reo is a surprisingly powerful mechanism for construction of connectors.
We demonstrate the expressive power of connector composition in Reo through
a number of examples.
Colloquiumcoördinator is Prof.dr. M. Aiello, Dr. M. Biehl (e-mail: M.Biehl@cs.rug.nl)