COMMENT ⊗   VALID 00002 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	parama[s84,jmc]		Parametrizing data bases
C00005 ENDMK
C⊗;
parama[s84,jmc]		Parametrizing data bases

	We often need to conclude that one subject is irrelevant to others.
We need to do this in order to restrict what facts we take into account
in solving some problem.  Here is one way it might be done.

Propositional calculus -

	Suppose we have an axiom involving a fairly large number
of propositional variables which represents what we know about some
subject.  It can happen that these variables are tightly connected
to one another, so there is no way of changing the values of
one or a few of the variables
without changing most of the others and still keep the axiom true.
At the other extreme, it may be that the variables divide into
groups, and the axiom is a conjunction of formulas, each involving
the variables of only one group.  Another possibility is that we
we have a master group and a dependent group.  There is no restriction
on the variables of the master group, but then the values of the
dependent group are determined.  Less favorable: the master variables
can be chosen independently, but then the dependent variables have
some freedom left.  What freedom depends on the values of the
master variables.

	It is also possible that there are no independent sets of
variables as it stands, but a "change of co-ordinates" can be made
such that in the new co-ordinates, the states are more independently
parametrized.

	What is known about this?

	Is Belnap's relevance logic relevant to this?