AW: Increasing interest in the HPSG conference

[Ivan A. Sag]

Hi Carl and Tibor (and Andrea :-))

>   My personal answer to Carl's question is as follows: quite
>   obviously, trees are what McCawley conceived them to be,
>   i.e. structural representations.
>
> But if it were so obvious, it would not be such a bone of contention.
> It SEEMED obvious to me too for many years, then I wondered about it
> for a few years, and now I believe it is false.

I've also come around to this view, but doesn't it entail that grammars cannot
include constraints that are stated over non-local structures?  Principle C in
GB or in Pollard and Sag 94 would be one such principle (even with the revised
formulation of o-command in PS-94, ch. 6).  I'm skeptical about Principle C
being a structural constraint, but I know there are others who would disagree.
Of course, Principle C could be simulated without appealing to trees as
structural representations, e.g. with pronoun stores of the sort explored by
Bach and Partee (1980).

> In response to my assertion
>
> > [GPSG] wasn't, as Uszkoreit and Peters proved. (The context-
> > freeness of GKPS was bought at the cost of imposing a linguistically
> > unmotivated prohibition on application of a given metarule more than
> > once in a derivation.)
>
> you replied
>
>   You seem to assume that the price to be paid for the restrictiveness was to
>   high.
>
> It is too high because it renders ungrammatical sentences like
>
>   A violin this well-crafted, even the most difficult sonatas are
>   easy [to play __ on __].
>
>   I have a personnel issue that I'm not sure who
>   [to talk to __ about __].

Wait a minute... You're going a little too fast for me.  The Peters/Uszkoreit
paper was about general properties of unconstrained `Metarule Phrase Structure
Grammars'. Your argument here seems to be presupposing a certain GPSG
analysis, one where SLASH-introduction is done by metarule, as in GKPS.
You're arguing that GPSG `bought context-freeness' only at the cost of
preventing the SLASH-introduction MR from applying to its own output (by
Finite MR Closure), thus disallowing, e,g.

      VP/{NP_1,NP_2} --> V[4] PP/{NP_1} PP/{NP_2} or maybe
      VP/NP_1/NP_2 --> V[4] PP/NP_1 PP/NP_2

But the PS-94 analysis of UDCs is GKPS-compatible, isn't it, assuming one adds
set-valued features to GPSG (as proposed by Maling and Zaenen 1983)?  And in
this case, the SLASH-introduction analysis would involve neither a metarule
nor a lexical rule, but it would allow multiple gaps.

I think the issue of context-freeness in GKPS is more complex.  Let's leave
aside the possible effect of `trans-derivational' well-formedness conditions
(e.g. those involving the notion of `privileged' instantiation of a local
structure, which requires inspection of all possible projections of a given ID
rule). Although GKPS might generalize out of the CFLs via metarules (by some
presumably mild relaxation of the finite closure condition), it could also do
so via the introduction of set-valued features, which is required in order to
make the PS-94 UDC analysis GKPS-compatible. Maybe there's some natural way to
make this generalization `mild'...


> If I remember correctly, there was no question of type vs. token-identity
> cropping up in GPSG.
> There weren't even AVMs in GPSG.
> >>
>
> This is true and to GPSG's credit, and I would advocate neither the type vs.
> token identity distinction nor AVMs.

> But I would not advocate trees qua structural representations either.

Is what you mean by this that:

(1) the theory contains identity constraints, period (feature
    values are either atoms or functions),
(2) there are no reentrant structures, and
(3) trees can be constructed, if needed, but there are no constraints
    in the theory that make reference directly to tree structures.

FWIW, these are the assumptions embodied in the formal bits of the SWB
textbook, which is GPSG-like in certain respects....

Best,
Ivan

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Ivan A. Sag
Professor of Linguistics and Symbolic Systems
Stanford University. Stanford, CA  94305
650-723-1578   (Stanford Ling Dept: 650-723-4284)

Email: sag at csli.stanford.edu
WWW: http://lingo.stanford.edu/sag/
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