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Mental Situations

As explained before, we use the concept of a mental situation in order to describe the internal state of a system as it reasons about a problem. A mental situation of STRIPS m is characterized by two atomic formulas: (1) GS(i,g,m) is true if subgoal g is at location i in the goal stack associated with m; (2) Current(m)=s is true if s is the current situation described by the database associated with m. Notice that, we do not need an explicit representation of the database associated with a mental situation, because axioms gif to gif allow us to compute such a database from the description of the current situation associated with that mental situation.

Axioms gif and gif describe how the initial mental situation tex2html_wrap_inline520 is constructed from the representation of a planning problem. The database associated with the initial mental situation describes tex2html_wrap_inline450 -the problem's initial situation. The goal stack contains a subgoalgif of the form tex2html_wrap_inline524 for each formula f that is in the stack describing tex2html_wrap_inline452 -the problem's goal situation- and is not in the database associated with the current situation (i.e., tex2html_wrap_inline532 ). The location numbers of the subgoals in the goal stack are the same as the location numbers of the formulas they refer to in the stack describing the problem's goal situation.


Josefina Sierra
Tue Jul 21 09:26:01 PDT 1998