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Morphological analysis
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The use of morphs in MITalk is unique, and it is responsible for much of the
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quality of the phonetic segment label sequences that are used for synthesis. There
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is no doubt that they introduce several levels of complication. These include the
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necessity of producing a morph lexicon and the need for a morph segmentation al-
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gorithm. The concatenation of morphs to form a word often gives rise to spelling
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mutations that cause segmentation difficulties, and several “morph coverings” of a
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word are often found leading to a need for selection criteria. Nevertheless, the
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gains far outweigh the negative costs, and in the following sections, we elaborate
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on these robust and effective techniques.
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3.2 Input
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In MITalk, morphemic analysis is provided in the DECOMP module. DECOMP’s
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input data stream has the same structure as the output stream from FORMAT
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which precedes DECOMP in the MITalk system. Each record in the data stream
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contains either a word or a punctuation mark. Words consist of uppercase letters,
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apostrophes, and/or hyphens. Legal punctuation marks are period, exclamation
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point, question mark, comma, semicolon, colon, double quotation, single quota-
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tion, left and right parentheses, and dash. DECOMP also accesses a compiled bi-
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nary format morph lexicon.
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3.3 Output
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The output data stream consists of a sequence of decomposed word records. The
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following information is contained in each record:
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1. Word spelling |
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2. Word part of speech (possibly more than one)
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3. For each part of speech, an optional list of part-of-speech features
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4., The series of morphs obtained by decomposition
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5. For each morph, the following information:
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a. Morph spelling
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b. Morph type
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c. One or two homographs
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d. For each homograph, a pronunciation and part(s) of speech
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If no decomposition was found for the word, then the morph list is omitted
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and the word is assigned a default set of possible parts of speech. Punctuation
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marks receive a special part-of-speech code (either EndPunctuationMark (EPM)
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for sentence-ending punctuation or InternalPunctuationMark (IPM) for all others).
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Part-of-speech processing will be described in detail in the next chapter where the
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phrase parser is discussed.
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27
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