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<Paper uid="C88-1023">
  <Title>LEXICON PHONOTACTI(&amp;quot; Hit T</Title>
  <Section position="2" start_page="107" end_page="108" type="metho">
    <SectionTitle>
4. Gonstr'ainin~ Principles
</SectionTitle>
    <Paragraph position="0"> Church discusses a number of factors, most of which date back to work by Morris Halle and are discussed by Chomsky and Halle /1960/, which must be taken into consideration when desl6ning the model I1983:1281 length, idiosyncratic systematic gaps, voicing assimilation, place assimi\].atien and dissimilation, sonority. These can all be incorporated very easily into the network. The fact that languages restrict sound combinations (Jdiosyncratlc gaps) and the length of initlal/flnal consonant clusters is in any case the basis on which this network is constructed. Decreasing sonority from the nucleus of the syllable towards the margins would seem to be a matter of having \[son\] as a C-feature and adjusting the value at the appropriate transition.</Paragraph>
    <Paragraph position="1"> With re~ard to phonotactic constraints, the C-.</Paragraph>
    <Paragraph position="2"> features on the transition labels may have variable values. In other words we may cater for the fact that all initial /s/ in Bn~lish may not be followed by voiced plosives by havin 5 as input specifications for one of its followln~ transitions the C-features {\[- voc\], \[~ cent\], \[~ voice\], \[o son\], \[- strid\]) (see Fig.2). ~ here must have the same value in the three cases, this value bein~ assigned durin}~ unification.</Paragraph>
    <Paragraph position="3"> Unification would fall in this case for voiced plosives as they would be specified for the feature~ {\[- reel, \[-cont\], \[+ voice\], \[- son\], \[- strld\]}. A further convention is Introduced, *tamely that once a feature has been specified on a particular transition it remains until it is eKplicitly altered, ell a subsequent transition. In this way vowel harmony may be incorporated into such a network whereby the vowel sDeeificatlons would remain for subsequent transitions since they would not be relevant for intervenin~ consonants.</Paragraph>
    <Paragraph position="5"> It shoal(l be clear also that feature bundle representation together with unification is an elegant way of dealing with assimilation, dissimilation and neutrallsation. Assimilation and dissimilation are dealt with by Chomsky and l{aile /1968/ in terms of variables a. ~\] feature cfK~.fficients and it is this , method which has been incorporated into the network here. So for example, in eases of voice assimilation, the fe/Iture \[voice\] may be checked using a variable, say \[a volc~\]. Therefore, where the particular input segment ha~ the feature \[+ voice\], unification assigns the value + to the undefinPSRl variable C/~ permanently, and slmilaFly in the case of a negative value. This newly found value together with the attribute will then be a (k-feature in the input specification for the following I ransltion unless exp\]icltly changed on that transition. This is a type of feature-passlng technique :~imilar to that employed in unification-based syn'i;actlc theories, but essentially simpler, slnce it is nsn-recurslve.</Paragraph>
    <Paragraph position="6"> Transltion weighting is also very important in this model, St\]kirk /1980/ emphasil~es that it is all very well to cater for collocational restrictions but other constraining principles such as maxlmising snoots should also) be incorporated into a syllable parser.</Paragraph>
    <Paragraph position="7"> Thus ironed\]ions are weighted in such a way that the most preferred path out of the network is sought.</Paragraph>
    <Paragraph position="8"> 'Early closure' /Kimball 1973/ :for example, which seeks the shorte~;t path out of the network, is equivalent to the maxima\[ onset principle. Str~s re~yllablflcatlon is simllar\]y dealt with using weighting. Thus, such constraints are incorporated into the network in a simple and principled fashitm.</Paragraph>
  </Section>
  <Section position="3" start_page="108" end_page="108" type="metho">
    <SectionTitle>
5. Gyllable Parsing
</SectionTitle>
    <Paragraph position="0"> Up to now we have \]men discussing the representation level, namely the phons\]attic net envisaged as a syllable template. The phonotacU.c net in hhls case was for English but it should be. clear that this representation may he used for other languages, dialects sr codes. Since the phenol~ctic net is a network of transduction relations between allophone and phoneme it should be both apeech analysia and synthesis.</Paragraph>
    <Paragraph position="1"> to note at this stage however, that level we are not re'~;tricte~ to what we employ. The phonotactic net may a usefu\[ tool for It is important on the processing parsing algorithm be interpretu~:l by any one of a number ~ff par,'~ing procedure.%. The .~;trategy emphJyed (i.e. depth-first, breadth first, hast fir.~t, ioskahead etc.) is~ a\].so totally independent of the repve~.~entation.</Paragraph>
    <Paragraph position="2"> In the mode\], deacrib(M here the aim wa~ to use the simplest formalism pcJssible. Thus the parsing and translation processes are undertaken by a deptl&gt;first nondeterministi.c finite state transducer. That is to say, the phonotacUc nets of ti-ansducti~n re\[atitms are interpreted by a fin~te,-state machine. Giwm the phonetic input in the form of feature bundles, the tram~ducer msve~; from ,,~tate to state in line ~ith the unification procedure de~;cr ilxM in s6x:tion '3 above. l':very time the tran,%duce.v reaches its fins} ,';tote gi &amp;quot;pC/~sible&amp;quot; sytlable ha,% been found. Therefore,in order to find more than one syllable the transducer iterates so that phonological units and syllable boundaries are output until the input ,qtring is empty. Thu~; we have a single iterative finite .%Late precooks. The parsing and canonicalisation pt-t~:e.~ses referred to in f;ection 2 abtwe are in(:orpora ted into a single proceduJ e. %that is interesting to note in this esnnection isl that since the l~Irsing proc+.~ture i.~; uondetermini~4tic in fact all &amp;quot;p(easible&amp;quot; syllables from the beginning of the input are checked internally (i.e. in the intermediate stag~ before producing ,mtput). Thu.~s the notion ell a &amp;quot;pov~slble ~ syllable of English is catered fol. From a psychological viewpoint it is an intere~ting fact that only the &amp;quot;possible&amp;quot; syl\]abh.,s aye considered. This would also be tile case in human protest, tog Iff neologisms whereby no attempt would be made to form a syllable with an \[mpc~sib\].e in ltJal/flnal consonant cluster comb\]no\]los: humans can accept w{wds which conform to the rules of their language even if the words do not actually exist. Thus, with thi:3 meg/el we can distlngnish Imtween &amp;quot;possible&amp;quot; and &amp;quot;acttlal&amp;quot; words. If we tested Currol\]'s Jabberwocky using this model we would get a correct syllable structure. As already noted, the lexictm filters out actual words.</Paragraph>
  </Section>
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