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Identity
The identity relation for a given language L is
. For a given pfsr
, the identity relation is given by the pfst
.
Note that it would be wrong to define
. Suppose
is true only of
. The pair
then would be true of the
pairs of symbols
, whereas identity requires that we only allow
the pairs
. Another
example to stress the point: the expression
identity(?) (`copy') is quite different from ?:? (`garbage-in
garbage-out').
It is therefore necessary to introduce an identity marker for each of
the transitions. The identity of a pfsr
is
given by
where
.
The operations domain, range and inverse are
straightforward. For a given pfst
,
we have:
Noord G.J.M. van
2001-06-22