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<Paper uid="W98-0902">
  <Title>Computing Declarative Prosodic Morphology</Title>
  <Section position="3" start_page="0" end_page="11" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Prosodic morphology (PM) circumscribes a number of phenomena ranging from 'nonconatenative' root-and-pattern morphology over infixation to various cases of reduplication, where the phonology strongly influences the shape of words by way of obedience to structural constraints defining wellformed morae, syllables, feet etc. These phenomena have been difficult to handle in earlier rule-based treatments (Sproat 1992, 159 ft.). Moreover, as early as Kisseberth (1970) authors have noted that derivational accounts of PM are bound to miss important linguistic generalizations that are best expressed via constraints.</Paragraph>
    <Paragraph position="1"> Kisseberth showed that verb stems in Tonkawa, a Coahuiltecan language, display a complex V/~ alternation pattern when various affixes are added (fig.</Paragraph>
    <Paragraph position="2"> 1). This leads to more and more complicated vowel deletion rules as the fragment is enlarged. In contrast, a straightforward constraint that bans three consecutive consonants offers a unified account of the conditions under which vowels must surface. Later devel'to cut' &amp;quot;to lick'</Paragraph>
    <Paragraph position="4"> opments have refined constraints such as ,CCC to refer to syllable structure instead: complex codas and onsets are disallowed. At least since Kahn (1976), Selkirk (1982), such segment-independent reference to syllable structure has been standardly assumed in the generative literature.</Paragraph>
    <Paragraph position="5"> Astonishing as it may be, even the latest computational models of PM phenomena apparently eschew the incorporation of real prosodic representations, syllabification and constraints. Kiraz (1996) uses multi-~tape two-level morphology to analyze some Arabic data, but - despite the suggestive title - must simulate prosodic operations such as 'add a mora' by their extensionalized rule counterparts, which refer to C or V segments instead of moras. There is no on-line syllabification and the exclusive use of lexically prespecified syllable-like symbols on a separate templatic pattern tape renders his approach vulnerable to postlexical resyllabification effects. Similarly, Beesley (1996) seems content in employing a great number of CV templates in his large-scale finite-state model of Arabic morphology, which are intersected with lexical roots and then transformed to surface realizations by various epenthesis, deletion and assimilation rules. Beesley states that further application of his approach to e.g. Hebrew is foreseen. On the downside, however, again there is no real prosody in his model; the relationship between template form and prosody is not captured.</Paragraph>
    <Paragraph position="6"> Optimality Theory (OT, Pnnce &amp; Smolensky 1993), as applied to PM (McCarthy &amp; Prince 1993), does claim to capture this relationship, using a  ranked set of violable prosodic constraints together with global violation minimization. However, to date there exist no sufficiently formalized analyses of nontrivial PM fragments that could be turned into testable computational models. The OT framework itself has been shown to be expressible with weighted finite-state automata, weighted intersection and bestpath algorithms (Ellison 1994) if constraints and OT's GEN component - the function from underlying forms to prosodified surface forms - are regular sets. A recent proposal by Karttunen (1998) dispenses with the weights while still relying on the same regularity assumption. Published PM analyses, however, frequently make use of constraint * parametrizations from the ALIGN family, which requires greater than regular power (Ellison 1995).</Paragraph>
    <Paragraph position="7"> Further developments of OT such as correspondence theory - extensively used in much newer work on PM - have not received a formal analysis so far. Finally, although OT postulates that constraints are universal, this metaconstraint has been violated from the outset, e.g. in presenting Tagalog -um- as a language-specific parameter to ALIGN in Pnnce &amp; Smolensky (1993). Due to the convincing presentation of a number of other forceful arguments against constraint universality in Ellison (to appear), the case for language-specific constraints must clearly be seen as reopened, and - as a corollary - the case for constraint inviolability as well.</Paragraph>
    <Paragraph position="8"> Declarative Phonology (DP, Bird 1995, Scobbie 1991 ) is just such a constraint-based framework that dispenses with violability and requires a monostratal conception of phonological grammar, as compared to the multi-level approaches discussed above. Both abstract generalizations and concrete morphemes are expressed by constraints. DP requires analyses to be formally adequate, i.e. use a grammar description language with formal syntax and semantics. As a consequence, Chomsky's crteda for a generative grammar which must be &amp;quot;perfectly explicit&amp;quot; and &amp;quot;not rely on the intelligence of the understanding reader&amp;quot; (Chomsky 1965, 4) are automatically fulfilled. DP thus appears to be a good starting point for a restrictive, surface-true theory of PM that is explicitly computational. null The rest of this paper reviews in informal terms the theory of Walther (1997) (section 2), showing in formal detail in section 3 how to implement a concrete analysis of Modern Hebrew verbs. Section 4 explains a novel approach to both generation and parsing of word forms under the new theory. The paper concludes in section 5.</Paragraph>
  </Section>
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