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<Paper uid="P00-1028">
  <Title>A Constraint-based Approach to English Prosodic Constituents</Title>
  <Section position="4" start_page="1" end_page="1" type="metho">
    <SectionTitle>
AZ
</SectionTitle>
    <Paragraph position="0"> The type of value of PHON is pros (i.e., prosody).</Paragraph>
    <Paragraph position="1"> In this paper, I am going to take word forms as phonologically simple. This means that the prosodic type of word forms will be maximal in the hierarchy.</Paragraph>
    <Paragraph position="2"> The only complex prosodic objects will be metrical trees. The minimum requirements for these are that we have, first, a way of representing nested prosodic domains, and second, a way of marking the strong element (Designated Terminal Element; DTE) in a given domain.</Paragraph>
    <Paragraph position="3"> Before elaborating the prosodic signature further, I need to briefly address the prosodic status of monosyllabic function words in English. Although these are sometimes classified as clitics, Zwicky (1982) proposes the term Leaners. These &amp;quot;form a rhythmic unit with the neighbouring material, are normally unstressed with respect to this material, and do not bear the intonational peak of the unit. English articles, coordinating conjunctions, complementizers, relative markers, and subject and object pronouns are all leaners in this sense&amp;quot; (Zwicky, 1982, p5). Zwicky takes pains to differentiate between Leaners and clitics; the former combine with neighbours to form Phonological Phrases (with juncture characterized by external sandhi), whereas clitics combine with their hosts to form Phonological Words (where juncture is characterized by internal sandhi).</Paragraph>
    <Paragraph position="4"> Since Leaners cannot bear intonational peaks, they cannot act as the DTE of a metrical tree.</Paragraph>
    <Paragraph position="5"> Consequently, the value of the attribute DTE in a metrical tree must be the type of all prosodic objects which are not Leaners. I call this type full,and it subsumes both Prosodic Words (of type p-wrd) and metrical trees (of type mtr). Moreover, since Leaners form a closer juncture with their neighbours than Prosodic Words do, we distinguish two kinds of metrical tree. In a tree of type full-mtr, all the daughters are of type full, whereas in a tree of type lnr-mtr, only the DTE is of type full.</Paragraph>
    <Paragraph position="6">  In terms of the attribute-value logic, we therefore postulate a type mtr of metrical tree which introduces the feature DOM (prosodic domain) whose value is a list of prosodic elements, and a feature DTE whose value is a full prosodic object:</Paragraph>
  </Section>
  <Section position="5" start_page="1" end_page="1" type="metho">
    <SectionTitle>
AZ
</SectionTitle>
    <Paragraph position="0"> Fig 2 displays the prosodic signature for the grammar. The types lnr-mtr and full-mtr specialise the appropriateness conditions on mtr, as discussed above.</Paragraph>
    <Paragraph position="1"> Notice that in the constraint for objects of type lnr-mtr, A8 is the operation of appending two lists.</Paragraph>
    <Paragraph position="2"> Since elements of type pros can be word-forms or metrical trees, the DOM value in a mtr can, in principle, be a list whose elements range from simple word-forms to lists of any level of embedding. One way of interpreting this is to say that DOM values need not obey the Strict Layer Hypothesis (briefly mentioned in Section 2.1 above).</Paragraph>
    <Paragraph position="3"> To illustrate, a sign whose phonology value corresponded to the metrical tree (6) (where the word this receives narrow focus) would receive the representation in Fig 3.</Paragraph>
  </Section>
  <Section position="6" start_page="1" end_page="2" type="metho">
    <SectionTitle>
3 Associating Prosody with Syntax
</SectionTitle>
    <Paragraph position="0"> In this section, I will address the way in which prosodic constituents can be constructed in parallel with syntactic ones. There are two, orthogonal, dimensions to the discussion. The first is whether the syntactic construction in question is head-initial or head-final. The second is whether any of the constituents involved in the construction is a Leaner or not. I will take the first dimension as primary, and introduce issues about Leaners as appropriate.</Paragraph>
    <Paragraph position="1"> The approach which I will present has been implemented in ALE (Carpenter and Penn, 1999), and although I will largely avoid presenting the rules in ALE notation, I have expressed the operations for building prosodic structures so as to closely reflect the relational constraints encoded in the ALE grammar.</Paragraph>
    <Section position="1" start_page="1" end_page="1" type="sub_section">
      <SectionTitle>
3.1 Head-Initial Constructions
</SectionTitle>
      <Paragraph position="0"> As far as head-initial constructions are concerned, I will confine my attention to syntactic constituents which are assembled by means of HPSG's Head- null in Fig 4. The ALE rendering of the rule is given in (7).</Paragraph>
      <Paragraph position="2"> mkMtr([HdPhon|PhonList], MoPhon)).</Paragraph>
      <Paragraph position="3"> The function mkMtr (make metrical tree) (encoded as a relational constraint in (7)) takes a list consisting of all the daughters' phonologies and builds an appropriate prosodic object ph. As the name of the function suggests, this prosodic object is, in the general case, a metrical tree. However, since metrical trees are relational (i.e., one node is stronger than the others), it makes no sense to construct a metrical tree if there is only a single daughter. In other words, if the head's COMPS list is empty, then the argument mkMtr is a singleton list containing only the head's PHON value, and this is returned unaltered as the function value.</Paragraph>
      <Paragraph position="4"> (8) mkMtr(CW 1 [pros]CX)= 1 The general case requires at least the first two elements on the list of prosodies to be of type full, and builds a tree of type full mtr.</Paragraph>
      <Paragraph position="5">  Note that the domain of the output tree is the input list, and the DTE is just the right-hand element of the domain. (10) shows the constraint in ALE notation; the relation rhd DTE/2 simply picks out the last  element of the list L.</Paragraph>
      <Paragraph position="6"> (10) mkMtr(([full, full|_], L), (full_mtr, dom:L, dte:X)) if  rhd_DTE(L, X).</Paragraph>
      <Paragraph position="7"> Examples of the prosody constructed for an N-bar and a VP are illustrated in (11)-(12). For convenience, Iuse[of the samurai] to abbreviate the AVM representation of the metrical tree for of the samurai, and similarly for [a cloak]and[at the collar].  pronominal NP occurring within a VP. Zwicky (1986) develops a prosodically-based account of the distribution of unaccented pronouns in English, as illustrated in the following contrasts: (13) a. We took in the unhappy little mutt right away.</Paragraph>
      <Paragraph position="8"> b.*We took in h V im right away.</Paragraph>
      <Paragraph position="9"> c. We took h V im in right away.</Paragraph>
      <Paragraph position="10"> (14) a. Martha told Noel the plot of Gravity's  their own right if they bear accent; unaccented pronominals must combine with a host to be admissible. Zwicky's constraints on when this combination can occur are as follows: (15) A personal pronoun NP can form a prosodic phrase with a preceding prosodic host only if the following conditions are satisfied: a. the prosodic host and the pronominal NP are sisters; b. the prosodic host is a lexical category; c. the prosodic host is a category that governs  combine to form a lnr-mtr, followed by any other material on the input list. Because of the way in which this prosodic constraint is associated with the Head-Complement Rule, the prosodic host in (16), namely the p-wrd tagged 1 , is automatically the syntactic head of the construction. As a result, Zwicky's conditions in (15) fall out directly. (17)-(18) illustrate the effects of the new clause. In the first case, the lnr-mtr consisting of told and it is the only item on the list in the recursive call to mkMtr in (16), and hence the base clause (8) in the definition of mkMtr applies. In the second case, there is more than one item on the list, and the lnr-mtr becomes a subtree in a larger metrical domain.</Paragraph>
      <Paragraph position="11">  it fail to parse, since (16) only licenses a head-initial lnr-mtr when the Leaner immediately follows the head. We could however admit told Noel ' it, if the lexicon contained a suitable entry for accent-bearing</Paragraph>
      <Paragraph position="13"> prosody of type p wrd, since this would satisfy the requirement that only prosodies of type full can be the value of a metrical tree's DTE.</Paragraph>
    </Section>
    <Section position="2" start_page="1" end_page="2" type="sub_section">
      <SectionTitle>
3.2 Head-Final Constructions
</SectionTitle>
      <Paragraph position="0"> To illustrate head-final constructions, I will focus on NP structures, considering the combination of determiners and prenominal adjectives with N-bar phrases. I take the general case to be illustrated by combining a determiner like this with a phrase like treasured possession to form one metrical tree. Since treasured possession will itself be a metrical tree, I introduce a new, binary, function for this purpose, namely extMtr (extend metrical tree) which adds a new prosodic element to the left boundary of an existing tree. For convenience, I will call the leftmost argument of extMtr the extender.</Paragraph>
      <Paragraph position="1"> Fig 5 illustrates the way in which extMtr is used to build the prosody of a specifier-head construction, while (19) provides the definition of extMtr.An example of the output is illustrated in (20).</Paragraph>
      <Paragraph position="2">  However, there are now a number of special cases to be considered. First, we have to allow that the head phrase is a single Prosodic Word such as possession, rather than a metrical tree. Second, the prosodic structure to be built will be more complex if the head phrase itself contains a post-head complement, as in treasured possession of the samurai. Crosscutting this dimension is the question of whether the extender is a Leaner, in which case it will form a lnr-mtr with the immediately following element. We will look at these cases in turn.</Paragraph>
      <Paragraph position="3"> (i) The head is a single Prosodic Word When the second prosodic argument of extMtr is not in fact a metrical tree, it calls mkMtr to build a new metrical tree. Definition (21) is illustrated in (22).</Paragraph>
      <Paragraph position="4">  the most awkward kind of mismatch between syntactic and prosodic structure arises when when the complement or postmodifier of a syntactic head is 'promoted' to the level of sister of the constituent in which the head occurs; this creates a disjuncture between the lexical head and whatever follows. Fig 6 gives a typical example of this phenomenon, where the noun possession is followed by a prepositional complement, while Fig 7 represents the prosodic constituency.</Paragraph>
      <Paragraph position="5"> Let's consider how treasured should combine with possession of the samurai. The Head-Complement Rule will have built a prosodic structure of the form [possession [of the samurai]] for the latter phrase. To obtain the correct results, we need to be able to detect that this is a metrical tree M whose leftmost element is a lexical head (by contrast, for example, with the structure [treasured possession]). In just this case, the extender can not only extend M but also create a new subtree by left-associating with the lexical head.</Paragraph>
      <Paragraph position="6">  The required definition is shown in (23) and illustrated in example (24).</Paragraph>
      <Paragraph position="7">  The special prosodic status of lexical heads is incorporated in Selkirk's (1981) notion of ph-phrase, and subsequent developments thereof, such as (Selkirk, 1986; Nespor and Vogel, 1986).</Paragraph>
      <Paragraph position="8">  the syntactic information associated with the leftmost element P of that tree. That is, if P is the phonology of the lexical head of the phrase, then it can be prosodically disjoined from the following material, otherwise the metrical tree M is extended in the standard way.</Paragraph>
      <Paragraph position="9"> There are various ways that this sensitivity to syntactic role might be accommodated. One option would to inspect the DTRS (daughters) attribute of a sign. However, I will briefly sketch the treatment implemented in the ALE grammar, which does not build a representation of daughters. Instead, I have introduced an attribute LEX inside the value of HEAD which is constrained in the case of lexical items to be token-identical to the PHON value. For example, the type for possession is approximately as follows:  any phrase projected from that head, and allows the PHON value of the lexical head to be accessed at that projection; i.e., headed phrases will also bear a specification [LEX phon], which can be interpreted as saying &amp;quot;my lexical head's phonology value is phon&amp;quot;. In addition, we let the function extMtr in Fig 5 take as an extra argument the HEAD value of the mother, and then test whether the leftmost Prosodic Word in the metrical tree being extended is the same as the LEX value of the mother's HEAD value.</Paragraph>
      <Paragraph position="10"> (iii) Extending the head with a Leaner Finally, there is an additional clause to accommodate the case where the extending element is a Leaner. This triggers a kind of left association, in that the result of combining a with [treasured possession]isastructure of the form [[a treasured] possession].</Paragraph>
      <Paragraph position="11">  This will also allow an unaccented subject pronoun to left-associate with the lexical head of a VP, as in [[he provoked][the objections of everyone]] (Gee and Grosjean, 1983).</Paragraph>
    </Section>
  </Section>
  <Section position="7" start_page="2" end_page="2" type="metho">
    <SectionTitle>
4 Concluding Remarks
</SectionTitle>
    <Paragraph position="0"> I believe that the preceding analysis demonstrates that despite the well-known mismatches between syntactic and prosodic structure, it is possible to induce the required prosodic structures in tandem with syntax.</Paragraph>
    <Paragraph position="1"> Moreover, the analysis retains rather conventional notions of syntactic constituency, eschewing the non-standard syntactic constituents advocated by Prevost and Steedman (1993), Steedman (1990; 1991).</Paragraph>
    <Paragraph position="2"> Although I have only mentioned two syntactic rules in HPSG, the radically underspecified nature of these rules, coupled with rich lexical entries, means that the approach I have sketched has more generality than might appear at first. With the addition of a rule for prenominal adjectives, prosodically interpreted like the Head-Specifier Rule, we can derive a range of analyses as summarised in (27). Here, I use square brackets to demarcate trees of type full-mtr and parentheses for trees of type lnr-mtr.</Paragraph>
    <Paragraph position="3"> (27) a. [this possession](of the samurai) b. [this treasured possession](of the samurai) c. (a treasured) possession d. (a treasured) possession [(of these) people] e. Kim gave (the book) (to the boy) f. Kim (gave it) (to the boy) g. Kim is happy [about Lee] h. Kim is happy [(that Lee) is fond (of the bird)] i. Kim wanted (to rely) (on the report) [(that Lee) is fond (of the bird)] It would be straightforward to augment the grammar to accommodate post-modifiers of various kinds, which would behave prosodically like post-head complements. By contrast, auxiliaries do not conform to the association between headed structures and prosodic structures that we have seen so far. That is, if auxiliaries are a subtype of complement-taking verbs, as assumed within HPSG, then they depart from the usual pattern in behaving prosodically like specifiers rather than heads.</Paragraph>
    <Paragraph position="4"> There are numerous directions in which the current work can be extended. In terms of empirical coverage, a more detailed account of weak function words seems highly desirable. The approach can also be tested within the context of speech synthesis, and preliminary work is underway on extending the Festival system (Black and Taylor, 1997) to accept input text marked up with metrical trees of the kind presented here. In the longer term, the intention is to integrate prosodic realisation within the framework of an HPSG-based concept-to-speech system.</Paragraph>
  </Section>
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