1. An information processing system for architecture model for interfacing with humans, said architectural model having a plurality of software modules divided into independent element functions, and a work memory area for reading and writing various information as a shared medium, said information processing system comprising: work memory area management means for managing history of task phase descriptions delivered to the work memory area as context information; a bid arbiter means, operably coupled to said work memory area management means, for receiving bids in a contract net protocol, for receiving context information accumulated by said work memory area management means, for evaluating bids in said contract net protocol using the context information, and for performing condition branching based on the bid evaluation in a contract net protocol; a dialog manager means for explaining a course of processing to a user and for providing means to customize the processing to the user, said processing being context information dependent, wherein said software modules communicate with each other by inputting and outputting said task phase descriptions to and from the work memory area by way of said work memory area management means, wherein said software modules operate based on the results of the bid evaluation, and wherein contract bidding is executed in accordance with a task to be executed when the bid is successfully awarded and in the form of bid-context condition strings showing a preceding processing needed for a planned task to be executed.