17 "TO SAY AND TO DO" VIRTUAL ACTIONS IN THE STRUCTURE AND RECOGNITION OF DISCOURSE PLANS WITH REGARD TO PRACTICAL PLANS Cristiano Casteljranchi*+ and Rino Falcone+ +National Research Council -Institute ofPsychology Finalized Project "Information Systems and Parallel Computation" * University of Siena - Multi-Media Lab CRIS@PSCS2.IRMKANT.RM.CNR.IT or F ALCONE@VAXIAC.IAC.RM.CNR.IT KEYWORDS: Plan Recognition, Computer Supported Cooperative Work (CSCW). ABSTRACT Cooperative activity requires both communication and execution of practical actions. Cooperative Works cannot be supported by obliging users to explicitly describe what they are doing and without understanding the relationships between what they discuss about and what they are doing. Furthermore, users cannot be oblige to send explicit messages to understand each other. We claim that in CSCW the system's capability of understanding actions, in particular of recognising plans and intentions, will play a fundamental role. We focus on the capability of recognising the correspondence between the plans agreed upon by the agents (Virtual Plans) and the ones they perform. This problem is particularly significant for the Action Workflow Approach. 1. INTRODUCTION Recently, critical judgements about the CSCW systems based on the analysis of conversations and Speech Act Theory have been growing more and more; in particular, attention has been focused on limits such as unnaturalness and coercion [Suc94, Bog9l] made their appearance. These limits can be brought back to different reasons (for instance Suchman herself ascribes them to the inadequacy of Speech Act Theory). In our opinion, the inner artificiality of these systems should not be ascribed to its background theory, but to the fact that the user is obliged to explicit each time (and, as a consequence, to classify) every act the user himself intends to do. This obligation is very unnatural, and the same holds for the obligation to declare explicitly the accomplishment of the task and to erase the commitment from the "agenda". This obligation derives from the necessity to match declarations with activities. In fact, cooperative activity requires both communication and execution of practical actions. But there is a special relation between conversations and actions: they should be coherent, they should match with each other. You cannot support cooperative work by obliging users to explicitly describe what they are doing and without understanding the relationships between what they discuss about and what they are doing. You cannot support cooperative work by obliging users to send explicit messages to understand each other. To cooperate in natural conditions, humans use not only communication (sending messages), but also their implicit domain knowledge and the interpretation of the behaviour of the partners. They are able to understand each other without explicit communication. How to cope with this problem of coercive explicitation in CSCW systems ? In our view, a quite hard way, that cannot be easily avoided, consists in the gradual introduction of comprehension capacities into the system. In general, we can say that the HM interaction systems are necessarily inclined to force human interaction and cooperative work in the machines' own schemes. On one side, human beings are coordinated in their actions by means of two instruments which are equally fundamental: message sending and the observation of others' actions. On the other side, machines just interact by means of the adequate message sending. Therefore the problem lies in of allowing the user of the HC system not to submit to this machine characteristic: We must find ways and forms to endow machines with the capability of receiving and understanding the information about what has been done in an interaction. The development of multimedia technologies will contribute to the solution of this problem especially K. Nordby et al. (eds.), Human- Computer Interaction © IFIP International Federation for Information Processing 1995