A Nonmonotonic Observation Logic
Frans Voorbraak

Abstract:
A variant of Reiter's default logic is proposed as a logic for reasoning with
(defeasible) observations. Traditionally, default rules are assumed to 
represent generic information and the facts are assumed to represent specific 
information about the situation, but in this paper, the specific information 
derives from defeasible observations represented by (normal free) default 
rules, and the facts represent (hard) background knowledge. Whenever the 
evidence underlying some observation is more refined than the evidence 
underlying another observation, this is modelled by means of a priority 
between the default rules representing the observations. We thus arrive at an 
interpretation of prioritized normal free default logic as an observation 
logic, and we propose a semantics for this observation logic. Finally, we 
discuss how the proposed observation logic relates to the multiple extension 
problem and the problem of sensor fusion.