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||Patrick Doherty and Jonas Kvarnström
||Tackling the Qualification Problem using Fluent Dependency Constraints:
||Recently, a great deal of progress has been made using nonmonotonic
temporal logics to formalize reasoning about action and change. In particular,
much focus has been placed on the proper representation of non-deterministic
actions and the indirect effects of actions. One popular approach to representing
the indirect effects of actions has been via the use of causal rules which in a more general sense can be viewed as fluent dependency constraints.
Although fluent dependency constraints have been used primarily under a
loose causal interpretation, we show that when interpreted in a broader
sense they provide a flexible means for dealing with a number of other representational
problems such as the qualification problem and the ramification constraints
as qualification constraints problem, in addition to the standard ramification
problem. More importantly, the use of fluent dependency constraints for
different purposes does not involve additions to the base nonmonotonic temporal
logic, TAL, used here, but simply the addition of several macro operators
to an action language used to represent action scenarios or narratives.
The payoff is that TAL has already been shown to offer a robust approach
to representing action scenarios which permit incomplete specifications
of both state and the timing of actions, non-deterministic actions, actions
with duration, concurrent actions, use of both boolean and non-boolean fluents,
and solutions to the frame and ramification problems for a wide class of
action scenarios. In addition, all circumscribed action scenarios in these
classes and the more general class involving qualification considered in
this paper can be shown to be reducible to the first-order case. Finally,
a restricted entailment method for this new class of scenarios is fully
implemented. In the paper, we present a challenge example which incorporates
all these features, propose a distinction between weak and strong qualification with a representation of both, and provide a visualization
of the preferred entailments using a research tool VITAL for querying and
visualizing action scenarios.
||The last 5 pages (number 10 to 14) are in color, and it is
recommended to print them using a color printer.
||Linköping University Electronic Press
|No. of pages:
||Linköping Electronic Articles in Computer and Information Science
|REFERENCE TO THIS PAGE:
|Doherty, Patrick and Kvarnström, Jonas (1997). Tackling the Qualification Problem using Fluent Dependency Constraints:
Preliminary Report in Linköping Electronic Articles in Computer and Information Science, Vol. 2. http://www.ep.liu.se/ea/cis/1997/016/.