Safeguard to control the behaviour of Task-Based Systems

First generation rule-based systems benefit of a lot of works and mathematical results. However they also have some limitations, often due to the implicit feature of their control. It is why, specific modelling primitives, like problem-solving methods and tasks, have been introduced in task- based frameworks in o rder to elicit t he problem- solving p rocess. However until now, no rigorous guaranties are offered about the dynamic behaviour of task-based systems. MetaTask is a knowledge- based system framework specially d esigned to provide a n explicit representation o f the c ontrol i n knowledge-based systems, while e nsuring "right" behavioural properties. MetaTask b enefits of a formal specification and o f a meta-layer, which have made possible the proofs of termination, correctness and semi-completeness. This paper presents the basic principles of MetaTask and sketch these behavioural proofs.