Reentrancy in feature structures

[John Beavers]

On Wed, 3 Jul 2002, Carl Pollard wrote:

> I hope not, since in my current research I have foresaken the
> graphical implementation of feature structures in favor of a treatment
> in terms of higher order logic. In the models this means feature
> structure types are indexed product types and the feature structures
> themselves are members of those types.  Thus there is only plain old
> equality (EQ), nothing corresponding to EQUAL. This makes some things
> (such as formalizing set values and distinguishing neutralization from
> ambiguity) much easier, but also means that coindexing cannot be
> handled the same way as in HPSG.

Maybe I missed something, but why would coindexing be that much different?
I agree the mechanism will be different for determining when two things
are "coindexed" but considering the entire mechanism of determing when two
things are EQUAL has been replaced with EQ, then that's expected.  But it
seems that once you nail a mechanism for coindexing things could work much
the same as in HPSG.  Or maybe I did miss something.

Best,
John