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A Foundational Theory of Contracts for Multi-party Service Composition

100%

Bravetti M. , Zavattaro G.

2008

tom Vol. 89, nr 4

451-478

In the context of Service Oriented Computing, contracts are descriptions of the observable message-passing behavior of services. Contracts have been already successfully exploited to solve the problem of client/service composition. Inspired by current orchestration languages, we consider services where the choice to perform an output may not depend on the environment. Under this assumption, we propose a new theory of contracts which also addresses the problem of composition of multiple services (not only one client with one service). Moreover, we relate our theory of contracts with the theory of must testing pre-order (interpreted as a subcontract relation) and we show that a compliant group of contracts is still compliant if every contract is replaced by one of its subcontracts.

Supporting Secure Coordination in SecSpaces

80%

Gorrieri R. , Lucchi R. , Zavattaro G.

2006

tom Vol. 73, nr 4

479-506

In this paper we investigate security problems which occur when exploiting a Linda-like data driven coordination model in an open environment. In this scenario, there is no guarantee that all the agents accessing the shared tuple space are trusted. Starting from a formalization of some typical security properties in the standard Linda coordination model, we present a novel data-driven coordination model which provides mechanisms to support the considered security properties. The first of these mechanisms supports logical partitions of the shared repository: in this way we can restrict the access to tuples stored inside a partition, simply by limiting the access to the partition itself. The second mechanism consists of adding to the tuples some extra information which permits to authenticate the producer of a tuple or to identify its reader/consumer. Finally, we support the possibility to define access control policies based on the kind of operations an agent performs on a tuple, thus discriminating between (destructive) input and (non-destructive) read permissions on each single tuple.

A Petri Net Based Modeling of Active Objects and Futures

80%

de Boer F. S. , Bravetti M. , Lee M. D. , Zavattaro G.

2018

tom Vol. 159, nr 3

197--256

We give two different notions of deadlock for systems based on active objects and futures. One is based on blocked objects and conforms with the classical definition of deadlock by Coffman, Jr. et al. The other one is an extended notion of deadlock based on blocked processes which is more general than the classical one. We introduce a technique to prove deadlock freedom of systems of active objects. To check deadlock freedom an abstract version of the program is translated into Petri nets. Extended deadlocks, and then also classical deadlock, can be detected via checking reachability of a distinct marking. Absence of deadlocks in the Petri net constitutes deadlock freedom of the concrete system.