Implementing contract net in tuple space models

Coordination is essential in distributed computing, which involves a group of loosely coupled agents cooperating in order to solve problems in a decentralised fashion. One of the popular approaches of coordination is the generative tuple space based communication, where agents interact via a shared data space. This paper discusses the implementation of Contract Net protocol (CNP) in a number of shared data space models, beginning with LINDA, and followed by several of its more secure variants. And finally, taking into account the importance of secure conversation in the process of task contracting, we propose the combination of Scope (a variant of LINDA) and access control attributes as the most appropriate model to be used as the mechanism in implementing CNP in the shared data space communication model. Apart from its tagging ability to limit visibilities and streaming property, the other significant advantages offered by Scope is its dynamicity (due to the scope-based operations), which is particularly useful in contracting several related tasks, where agents’ visibilities can be tailored (widened or limited) according to need. Incorporating attributes in the model provides a more secure contracting, without losing the flexibility offered by Scope.