Commentary on Bird and Klein 
Richard Sproat 1 
(AT&T Bell Laboratories) 
As Bird and Klein rightly observe, phonological thinking has lagged behind that in 
syntax and semantics: the metaphor of underlying representations being transformed 
via an ordered set of rules, long abandoned in syntax, is deeply ingrained in phonol- 
ogy. The cleanest break with this tradition is represented by declarative phonology, of 
which the current paper is an instance; indeed, the adoption of an HPSG-style typed- 
feature formalism makes it clear how much Bird and Klein want phonology to be 
like syntax. Now, the HPSG formalism is just that, a formalism. It neither is a the- 
ory of phonology per se (the theory consisting in constraints statable in terms of the 
formalism), nor does it imply anything about the actual implementation, which they 
envision in terms of Bird and Ellison's one-level phonology model: a crucial property of 
both the theory and its implementation is that it be one-level, since this avoids the 'rule 
conspiracies' inherent in multi-level models. Bird and Klein exemplify the approach 
with two detailed case studies, which give a good sense of the range of phenomena 
that are amenable to a one-level analysis. At one extreme is Sierra Miwok templatic 
morphology, which few phonologists would now analyze using rewrite rules, and 
where a standard autosegmental analysis is already largely declarative. At the other 
is French schwa 'deletion,' which is interesting because the phenomenon seems to re- 
quire a rewrite rule. For Bird and Klein, the actual 'deletion' of schwa is handled by 
allowing schwa to be optional in lexical entries, with its appearance or nonappearance 
following from general properties of French syllable structure: a declarative one-level 
approach turns out to be more explanatory than a rule-based one. 
Nonetheless, I still have concerns about one-level phonology. Consider Xiamen 
tone sandhi (XTS) (Chen 1987). In an XTS domain, only the domain-final tone sur- 
faces in its 'underlying' form: all others must change according to a rule whereby, for 
example, the tonal sequence 1-2-3-4-5 surfaces as 7-1-2-8-5. Crucially, there is nothing 
ill-formed about 1-2-3-4-5 as a surface sequence of tones: it could represent (under- 
lying) 2-3-7-8-5, for example. It seems that XTS cannot be treated interestingly as a 
surface constraint, but must be viewed as a conditioned transduction between un- 
derlying and surface forms. And consider that multilevel models implemented using 
finite-state transducers are useful not only for describing phonological or orthographic 
regularities, but also the mapping between orthography and phonology. So, in a Rus- 
sian text-to-speech system, one might compute the pronunciation of the orthographic 
word CTOae (table-Prep.Sg.) by transducing it to a morphologically annotated repre- 
sentation (CTOa+6), which includes crucial accentual information; and then computing 
the pronunciation (/stalj6/) noting, for instance, that pre-accentual o is /a/ and not 
/o/. A multilevel model enables one to readily state relations between what must be 
viewed as different levels of representation for the same word. It remains to be shown 
how a one-level approach would work. 
References 
Chen, M. (1987). "The syntax of Xiamen tone 
sandhi." Phonology Yearbook, 4, 109-149. 
1 AT&T Bell Laboratories, Room 2d-451, Murray Hill, NJ 07974. E-mail: rws@research.att.com. 
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