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<Paper uid="C90-3050">
  <Title>Towards a Unification-Based Phonology</Title>
  <Section position="1" start_page="0" end_page="283" type="metho">
    <SectionTitle>
1 Introduction. The Problem
</SectionTitle>
    <Paragraph position="0"> Phonological theory has undergone a number cf more or less radical changes in recent years. Models of non-linear representation of features, constraints on the abstractness of rules, and theories of underspecification (imposing conditions on possible underlying features and their values, avoiding redundancy) are all part of current phonological thinking.</Paragraph>
    <Paragraph position="1"> Considerations of the formalisms involved in these theories have not been pursued to a large extent.</Paragraph>
    <Paragraph position="2"> !',. has become increasingly clear, however, that different representational formats lead to differences in the formalisms required for phonological rules. Recently, there have also been attempts to clarify the formal status of associations between elements cn different tiers (Sagey 1988, Hammond 19~8, Bird &amp; Klein 1989). This paper is an attempt to clarify some of the properties cf phonological rules and representations by applying the concepts of unification formalisms to phonological theory.</Paragraph>
    <Paragraph position="3"> A crucial part of any unification-based phonological theory is the elimination of feature-changing rules from the list of possible rules in the framework. Feature-changing rules stand in clear oppesitbn to the incremental, monotonic nature of unification grammars. In the following, it wilt be shown how a cLange of feature-values can be avoided for a rule which, first, is a regular phone-logical rule within any phonological theory that allows for phonological rules at all, and which, second, has always been formulated as a feature-changing rule (see literature from Kiparsky 1968 to Rubach 1990). t 2 A standard analysis of German Final Devoieing The rule in question is one of the classical examples of a neutralization rule, namely the rule of Final Devoicing (Auslautverh~'rtung, FD for short) in the phonology of Standard German. It neutralizes the phonemic contrast between voiced and unvoiced obstruents in a particular position (namely syllable-finally). The standard view of this rule is that it changes voiced obstruents in syllable-final position into their unvoiced counterparts. Examples are provided in (1), and a feature-changing version of this rule is given in (2). It is clear now that the relevant domain for the rule is the syllable (see Vennemann 1978, Wiese 1988); depending on the model of syllabic structure, the precise formulation of the context description can vary, referring to the syllable edge as in (2) or to the final constituent of the syllablefl  In (3), the application of the rule (2) is exemplified. Note that the rule changes the value of a feature. In the framework assumed, this is necessarily so, since in the \[- sonorant\]-class, voicing is distinctive, so that both/b/ and /p/ are assigned this feature. (4) demonstrates that a different syllabification (due to suffixation) correctly prevents FD from applying. 3  (3) (4) a. /lo:b/ a, /Io.b/ b. --- b. /lo:b / os/ c. 0 e. (J o d. o d.</Paragraph>
  </Section>
  <Section position="2" start_page="283" end_page="284" type="metho">
    <SectionTitle>
3 The alternative solution
</SectionTitle>
    <Paragraph position="0"> How could FD be formulated in a non-featurechanging way without giving up the goal of capturing all generalizations that hold for this rule? The following considerations rely on some (fairly uncontroversial) assumptions about phonological representation. First, in accordance with underspecifieation theory, it will be assumed that redundant feature values are not present in underlying representations (lexical entries). For the relevant segments this means that the voiced obstruents are marked as r+ voiced\], whereas unvoiced obstruents are not marked for this feature. General considerations of markedness support this choice: Voiceless obstruents are more common, have a wider distribution, are acquired earlier in language acquisition, etc.</Paragraph>
    <Paragraph position="1"> Secondly, all features, including those representing a segment, are represented in a non-linear, associative way. In particular, a hierarchical model of the segment in the version of McCarthy (1988: 105) is adopted. In this particular version of a feature hierarchy, all nodes are characterized by the presence of particular features that constitute the node. (5) is not quite complete, but allows the representation of most natural classes of segments. 4 (Conceivably, as argued by Goldsmith (1990: oh.</Paragraph>
    <Paragraph position="2"> 6.2), under assumptions of underspecification ,the feature hierarchy in (5) and in comparable proposals is too elaborate. For the present purposes, the only important assumption is that features and their values are organized hierarchically.) We will interpret the feature hierarchy in (5) as an admissibility tree. Features are only allowed if they enter the relations expressed in this tree. Furthermore, the relations (&amp;quot;associations&amp;quot; in the terminology of non-linear phonology) are interpreted as being transitive. The values of features are propagated (as instructions to the artiaulatory apparatus) along the paths specified by the relations to the root. In (6), the feature tree (5) is receded into a complex feature structure. Every feature takes as a vMue either one of the terminals (&amp;quot;+&amp;quot; or &amp;quot;-&amp;quot;) or another feature structure. Associations are ex-pressed by a feature A with the interpretation for tile associations as just given. (Different instances receive numerical indices.) As a template for possible segments, this structure does not contain the terminal values, i.e. + and -. These values are denoted by &amp;quot;\[\]% the empty feature structure, if unspecified. null</Paragraph>
    <Paragraph position="4"> Operations on feature trees or structures of this kind are very limited. We allow only the foliowing types of formal operations: - insertion of associationsfi - deletion of associations (&amp;quot;delinking&amp;quot;). The first operation generally occurs through unification. Unification here is the combination of lexical entries and regularities that are independently motivated and expressed as feature structures. The information in the feature structures is combined, leading to statements that particular relations hold. In particular, the assignment of default values for features is achieved through unifying the feature structures that express the default value with representations for lexical entries that do not contain a specified value for the respective feature. Dclinking, on the other hand, is not so readily modeled with unificational means (as presented by Shieber 1986 or Carlson &amp; Linden 1987); it can be seen, however, as the introduction of generaliz,~tion (&amp;quot;the dual of unification&amp;quot;, Shieber (1986: 64)) into the theory. Under generalization of two feature strucures, only information contained in both is kept; all other information is lost. We will now show that using generalization alongside unification allows us to state FD widmut the bvocation of a feature-changing rule.</Paragraph>
    <Paragraph position="5"> The typology of rules proposed here does not allow feature values to be changed. The treatment of FD in German, then, is the following. Taking /d/ and /t/as examples, marking for \[voiced\] is expressed underlyingly as in (7). 6 There exists a default rule (8) that in general (i. e., in the absence of other provisions) allows values for \[voiced\] to be identical to the value for the feature \[sonorant\]. This rule uses feature reentrancy. (Possibly, sonorancy itself is also underspecified, but this is left out of consideration here.) Furthermore, there is no rule of FD but a well-formedncss condition (9) which explicitly requires obstruents to be \[- voiced\] syllable-finally. (8) and (9) are short-hand notations for the more complex formulations within the leature structure. The crucial step in the derivation of, say, R,~lt\], with an underlying/d/, is the generalization of the two feature structures (7a) and (9), with different values for \[voiced\]. As a result, \[voiced\] is unspecified. (10) illustrates the steps in the application of the various mechanisms leading to the devoicing of /d/. The apparent change in the value vet \[voiced\] is possible because of generalization, which removes a value, and the existence of the default rule, which provides a value.</Paragraph>
    <Paragraph position="7"> Lvoiced: - syllable unification with (8) It nmst be stressed that this proposal for the treatment of FD has one major advantage over the traditional analysis: While it is clear that neutralization processes such as FD always disallow the more marked member of the pair in question, there is nothing in the formalism for the FD rule (2) that would formally disallow a rule that leads to the marked member of the pair. This, however, is impossible in the framework introduced here. If a wellformedness condition analogous to (9) would require a voiced obstruent syllable-finally, there would not be a rule which could provide the value \[+ voiced\]. There simply is no rule comparable to default rule (8). In other words, neutralization for \[voiced\] can only lead to \[- voiced\] because there is a well-motivated default rule providing this value. In this sense, the solution in the framework given has a higher explanatory level than the ones operating with a feature-changing rule, where both types of change, from marked to unmarked and from unmarked to marked, are equally complex.</Paragraph>
  </Section>
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