Reference Resolution - Man-Machine Dialogue: Design and Challenges - page 103

elements on this list. For such application elements, Duermael [DUE 94] uses
the term of operator, and defines it as an action model, made up of
preconditions, postconditions and a body. The body matches a function of the
application. The indispensable preconditions enable the system to check the
applicability of this function by checking, for example, that the objects in
question are indeed compatible with the function. The postconditions are used
to simulate the function's running, just before carrying it out: the goal is to
simulate the effects with transient representations of the objects and the
knowledge, so as to see what the objects and knowledge undergo and what
the result is. This anticipation allows the system, however, to detect problems
that are difficult to predict, for example collateral ones, and important, such
as the deletion of an object. If the system believes it is relevant, it can then
warn the user of the consequence and ask for confirmation. The anticipation
also allows it to implement a dynamic management of the action, and
implement a cancellation function, which is not necessarily easy when
deleting and modifying important objects.
An application function requires parameters. It is often applied to objects
according to very specific properties. An object movement function thus
requires knowing the object in question and the considered location, as well
as the preconditions of the fact that the object can be moved, and that it will
fit at its destination. To run, the function needs these two parameters. In the
simplest case, the user's utterance has a verb whose semantics are clearly
linked to that of the intentional operator and whose valency matches the
number of parameter required. This is the case for “move that there”: since
the two parameters are not of the same nature, the action's reference
resolution happens very simply. In other cases, for example with “I am
moving that there” or in “move that”, the reference resolution requires the
system either to ignore a parameter, since it is not in fact a parameter but only
a neutral expression with regard to the task to be carried out, or to detect the
absence of a parameter, which leads the system to query it. This is obviously
the most common case in train ticket reservation dialogues (and also why
thematic roles are identified during the semantic analysis), which the U1
example highlights: “I would like to go to Paris” does not mention the
departure station or the departure time, which are necessary parameters.
Faced with this utterance, the system can consider that the user is starting a
query which has to be completed by the dialogue together with the system.
The system can then plan the precision queries and start with the departure