9.1598, Review: Scobbie: Autosegmental Representation

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LINGUIST List:  Vol-9-1598. Fri Nov 13 1998. ISSN: 1068-4875.

Subject: 9.1598, Review: Scobbie: Autosegmental Representation

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1)
Date:  Thu, 12 Nov 1998 20:10:34 -0700 (MST)
From:  Mike Hammond <hammond at U.ARIZONA.EDU>
Subject:  Review: Scobbie: Autosegmental Representation

-------------------------------- Message 1 -------------------------------

Date:  Thu, 12 Nov 1998 20:10:34 -0700 (MST)
From:  Mike Hammond <hammond at U.ARIZONA.EDU>
Subject:  Review: Scobbie: Autosegmental Representation

	[**Editor's note, a version of this review with full graphics is
	available at the Web Page for this issue]

Scobbie, James M. (1997) Autosegmental Representation in a Declarative
    Constraint-Based Framework, Garland Press, New York. [Revision of
    1991 PhD dissertation, University of Edinburgh] (footnote*)

Reviewed by Michael Hammond, University of Arizona


	Jim Scobbie's dissertation, recently published in the
Outstanding Dissertations in Linguistics Series through Garland Press,
is an excellent example of a pre-Optimality-Theory attempt at a
constraint-based phonology that has received insufficient attention in
the phonological community. This is extremely unfortunate, as the
thesis makes a number of interesting proposals that are well worth
considering today.

	The dissertation is not in the usual vein of American
phonology theses.  It's not an in-depth analysis of some particular
array of data. Rather, it appears to fit a much more European
template, with more attention paid to placing the author's proposal in
the context of previous ideas. Despite this very different approach,
there is much to recommend it.

	The general hypothesis pursued is that phonological
generalizations and representations are best cast as attribute-value
structures. These formal devices are drawn from the HPSG (Head-Driven
Phrase-Structure Grammar) literature (Pollard & Sag, 1987). The basic
idea is that dominance is expressed as something roughly equivalent to
a featural distinction. For example, in a standard phonological
representation the fact that a vowel might be high is expressed by
assigning the vowel a '+' for a feature [high], e.g. [+high].
Expressed in attribute-value formalism, the attribute [high] has the
value '+'.  HPSG goes one step further and encodes dominance in the
same fashion. Thus, the fact that a syllable has a [+high] nucleus is
expressed by positing a nucleus attribute for a syllable element and
then allowing the nucleus attribute to itself have [+high] as an
attribute-value pair. (Figures are adjusted for ascii presentation.)

(1)	[onset ...
	nucleus [high +]]

The formal object above denotes a syllable with a [+high] nucleus. (I've
indicated irrelevant information with ellipses.)

	In the context of these representations, Scobbie's central
claim is that autosegmental association can be formalized as dominance
in an attribute-value structure. Phonological representations also
encode linear order, but in Scobbie's theory, linear order is
formalized only for root nodes (and is indicated with indices). A
string of segments would then be represented as a set of indexed root
matrices, essentially of the following sort.

(2)	{<i,[]>,<j,[]>,<k,[]>}

Indices are ordered by the relation IMMEDIATE PRECEDENCE '<*'. (footnote1)

	With these structures, Scobbie goes further and suggests that
phonological rules should be traded in for constraints. These
constraints, he suggests, are formally indistinct from the
representations they apply to. (A rather similar position has been
advanced in OT. See Russell, 1995 and Hammond, to appear.) For
example, a generalization excluding mid nasal vowels would be
expressed as follows.

(3)	NOT {[low -],[high -], [nasal +]}

Such an expression rules out an element which is simultaneously
specified [- low], [-high], and [+nasal].

	Constraints don't actually "apply" to representations. Rather,
Scobbie proposes, constraints are unified with
representations. Unification allows to representations to meld, just
so long as they don't conflict. For example, a representation
consisting solely of [+high] and one consisting solely of [- nasal]
can combine into [+high,-nasal]. However, a representation consisting
of [+high] cannot unify with one consisting of [-high]. (footnote2)
(Note how this would appear to rule out contour segments: more on this
below.)

	If two things do not unify, the result is ill-formed. A
negative constraint like the one in (3) above indicates that if it can
unify with a representation, then that representation is
ill-formed. The representation in (1) is equivalent to (4) and the
representation in (3) is equivalent to (5).

(4)	T -> [onset ..., nucleus [high +, ...]]

(5)	[low -, high -, nasal +] -> _|_

	Scobbie's claim is that all phonology can be treated in terms
of these representations and in terms of unification. This is a
dramatic and important hypothesis. However, as Scobbie himself notes,
there are lots and lots of apparent problems and lots of work to be
done. On the upside, the model is refreshingly simple and elegant.

	A very obvious question still to be answered is how to
indicate mapping relations. For example, one can stipulate in a
constraint that a nasal and following stop must share place of
articulation. However, one must go further and indicate where that
information comes from: the nasal or the following consonant. For
example, is /mt/ in some language realized as [mp] or as [nt]?  Both
results satisfy a constraint on homorganicity. There are a variety of
moves one could make here, but the theory offered does not make a
specific proposal.

	A central problem facing any theory of this sort as applied to
autosegmental phonology is the problem of reentrancy, how the same
autosegment can be associated to multiple anchors. Scobbie proposes to
represent this situation by making a distinction between types and
tokens. Specifically, he uses a different indexing scheme to indicate
that the same structure is shared by two different elements. For
example, the index variables below indicate that the two matrices
share the token value for A, but merely share the type value for B.

(6)	{<i,[A 1, B +]>,<j,[A 1, B +]>}

	Scobbie develops this formalism in a number of ways. First, he
argues that representations like the one above are subject to what he
calls the Sharing Constraint (p.93).

(7)	Sharing Constraint
	If a structure M=[] is dominated by two paths of type P with
	indices i and j, where i <* j, then for every index n where
	i <* n <* j there is a path <n,P> dominating M.

The immediate effect of this is to rule out cases where noncontiguous
root elements share a token value. Scobbie argues that the evidence
for such cases is weak. (Cf. a very similar proposal in Archangeli &
Pulleyblank, 1994.)

	A more interesting consequence is that Scobbie uses this
constraint in an attempt to derive the No-Crossing Constraint (NCC),
part of Goldsmith's (1976) more general Well-Formedness Condition on
autosegmental representations. This is the constraint that rules out
crossing autosegmental association lines.

	Sagey (1986; 1988) first proposes to derive the NCC from a
treatment of autosegmental association as overlap. However, Hammond
(1988) argues that this notion is formally problematic proposing a
different characterization of association as a transitive,
irreflexive, and asymmetric relation. Hammond's approach, however,
does not derive the NCC without stipulation. Scobbie's approach also
involves an asymmetric characterization of association (as dominance),
but does derive the NCC.

	Scobbie's derivation of the NCC is based on the assumption
that there are no contour values. That is, while two different root
nodes might share a value token as in the second picture below, one
root node cannot bear two different values, as in the first picture
below (where "S" indicates a segment or root node and "T" indicates a
tone or value token).

(8)	a.			b.
		T   T			   T
		 \ /			  / \
		  S			 S   S

This is a necessary position given his formalization of sequencing:
only root nodes bear an index for linear position; nonroot tokens are
unsequenced. (A similar position is developed in Heiberg, in prep.)
Were contour values to be allowed, there would be no way to
distinguish their ordering. On the other hand, when two root nodes
share a value, their ordering is distinguished in terms of indices, as
in (6).

	The upshot of the prohibition on contours is that violations
of the NCC can only arise when there is an independent Sharing
violation. That is, NCC violations look like (9), and (9) necessarily
includes a Sharing violation.

(9)	T  T
	 \/ \
	 /\  \
	S  S  S

This is a very nice result, but comes at the cost of i) ruling out
discontinuous association, and ii) excluding contour values.

	Scobbie also argues that his approach allows him to derive the
phenomenon of geminate integrity (Hayes, 1986; Schein & Steriade,
1986). The basic idea of geminate integrity is that geminates resist
epenthesis. (See Guerssel, 1977; 1978 for an early treatment and Suh,
1997 for a recent proposal.) The standard account of this is that
geminates resist epenthesis because the result would entail crossing
association lines, and a violation of the NCC, as in (9) above.

	The problem with this, as noted by Scobbie and others as well,
is that if the epenthetic vowel is featureless (10) or inserted on
another tier (11), then no violation of the NCC occurs.

(10)	C V C
	 \ /
	  T

(11)	  T
	  |
	C V C
	 \ /
	  T

	Scobbie's own proposal is simple and direct. Epenthesis into a
geminate structure results in a violation of Sharing, regardless
whether the epenthetic vowel has features or whether its features
might appear on some other tier.

	Scobbie goes on to consider the possibility that geminate
inalterability might also follow from the Sharing Constraint, but here
his proposal is a lot more speculative. The basic idea pursued is that
geminate inalterability results from default rules. The problem is
that Scobbie doesn't really offer a clear proposal on the nature of
default rules. On the face of it, they would seem to be a glaring
problem for the monotonic theory he proposes.

	In his final substantive chapter, Scobbie treats the problem
of long- distance association, as in, e.g. Arabic verbal
morphology. He offers some well- taken criticisms of the traditional
autosegmental approach, but does not really offer an explicit
declarative counterproposal.

	In sum, this book is well worth reading. It offers a very
interesting alternative constraint-based view of phonology with much
to recommend it. On the other hand, there are a number of unresolved
questions. What about floating segments? Scobbie speculates on this,
but offers no satisfying solution. As noted above, contour segments
are also ruled out, though the evidence for these in the tonal domain
is unimpeachable. (footnote3)

References

Archangeli, D. & D. Pulleyblank (1994) Grounded Phonology, MIT Press,
Cambridge.

Bird, S. (1995) Computational Phonology, Cambridge University Press,
Cambridge.

Goldsmith, J. (1976) Autosegmental Phonology, doctoral dissertation, MIT.

Guerssel, M. (1977) "Constraints on phonological rules", Linguistic
Analysis 3, 267-181.

Guerssel, M. (1978) "A condition on assimilation rules", Linguistic
Analysis 4, 225-254.

Hammond, M. (1988) "On deriving the Well-Formedness Condition", LI 19,
319-325.

Hammond, M. (to appear) "There is no lexicon!", Coyote Papers.

Hayes, B. (1986) "Inalterability in CV phonology", Language 62, 321-351.

Heiberg, A. (in prep) doctoral dissertation, U. of Arizona.

Pollard, C. & I. Sag (1987) Information-Based Syntax and Phonology, volume 1,
CSLI 13.

Russell, K. (1995) "Morphemes and candidates in Optimality Theory",
ms., U. of Manitoba, ROA.

Sagey, E. (1986) The Representation of Features and Relations in
Non-linear Phonology, doctoral dissertation, MIT.

Sagey, E. (1988) "On the ill-formedness of crossing association
lines", LI 19, 109-118.

Schein, B. & D. Steriade (1986) "On geminates", LI 17, 691-744.

Suh, C.-K. (1997) Consonant Geminates: Towards a Theory of Integrity
and Inalterability, doctoral dissertation, U. of Arizona.

Footnotes

* Thanks to Jim Scobbie for useful discussion. Any misinterpretations,
lapses, or other errors are my own.

1 Though as Scobbie (p.c.) points out, ordering these with precedence
instead will allow for a treatment of epenthesis, morphological
intercalation, and the like.

2 My expository characterization is procedural, but of course,
unification is not formally so.

3 A number of similar ideas are developed in Bird (1995).


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