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frame[f86,jmc]		The Frame Problem Today

For Frank Brown's Workshop on Logical Solutions to the Frame Problem

extended abstract due Dec 1
csnet csdept@ukans

	The frame problem was first posed in (McCarthy and Hayes 1969).
It is the problem of avoiding having to state what doesn't change when an
action occurs.  For example, if we have facts about moving blocks and
painting blocks, it is normally true that moving a block doesn't change
its color or that of any other block or the locations of other blocks, and
painting a block doesn't change the positions of any blocks and the colors
of blocks other than those painted.
When there are only a few actions and properties of objects it is possible
to give the required {\it frame axioms} explicitly.
Here they are for moving and painting blocks using the situation calculus.
In other formalisms the expressions could be expressed similarly.

  However, if we
are trying to build a general purpose database of common sense knowledge,
there will be a large number {\it m} of kinds of action and another
large number {\it n} of properties of objects, and it seems unreasonable
and even infeasible to write down the {\it mn} axioms that would be required.

	Moreover, human performance tells us that this must be unnecessary,
because we aren't conscious of large numbers of frame facts, and when
we describe the effects of actions to other people we don't include
large numbers of such facts in our oral or written discourses.

	The name {\it frame problem} came from one approach to the
problem based on an analog of the {\it co-ordinate frames} used in
mathematical treatments of geometry.  It is also analogous to the
concept of {\it assignment statement} used in computer programming.
If we attach the properties of objects to ``frames'' we can define
actions relative to the frames by asserting that no other properties
attached to the frames besides the ones listed.  Here is an example
of such axioms for moving and coloring blocks.