Assembling a Device

We present here a new way of reasoning on a device based on structure, we call assembling a device. It consists of a symbolic combination of local qualitative constraints (namely confluences) leading to more global relations. Some reference variables are selected according to the task to be performed (simulation, observation, postdiction,...). The assembling step produces a set of equations expressing directly “internal” quantities as functions of the reference quantities. We call such a set a task-oriented assemblage. Then, determining the non ambiguous variables for a particular assignment of the reference quantities turns out to be straightforward. We can thus expect to perform qualitative reasoning on large systems. The assembling tool is a new rule, we call the qualitative resolution rule. It has agreable properties: (1) interpretation: each application can be interpreted as joining local descriptions to more global ones; (2) completeness: an assemblage provides all the non ambiguous variables for any assignment. of reference variables.