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From text to speech: The MITalk system
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“Preprocessor” (Allen, 1968). The current algorithm goes right-to-left across the
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morphs and uses the part of speech of the rightmost morph for a compound, as
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well as for cases where there is a suffix. This is justified by two facts:
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1. suffixes (especially the rightmost suffix since it is outermost in the
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“nesting” of affixes) determine the part of speech of a word with
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regularity (e.g. ...ness is a NOUN);
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2. the part of speech of compounds is very idiosyncratic (in fact, it is
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usually determined by semantic rather than syntactic information)
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and the best heuristic is to use the part-of-speech set of the rightmost
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root.
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A complete description of the part-of-speech processor is given in Appendix
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A. First, the processor checks to see if there was a decomposition. If there is
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none, then it calls a routine which assigns the part-of-speech set (NOUN (NUM
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SING), VERB (PL TR) (INF TR), ADJ) unless the word ends in ’S in which case
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the part-of-speech set is (NOUN (POSS TR), NOUN (NUM SING) (CONTR
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TR)). Next, the program determines whether the last morph in the decomposition
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is a suffix. If it is not, then the program checks for the part-of-speech determining
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prefixes. The prefixes EM, EN, and BE indicate that a word is a VERB, while A
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gives the part-of-speech set (ADJ, ADV). (Suffixes have priority over these, as in
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befuddlement.) If none of these are present, then the processor assigns the part-
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of-speech set of the last morph in the decomposition.
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The rest of the processor is essentially a dispatch on the last suffix. In many
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cases, the next to last morph’s part of speech must also be examined. If the last
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morph is the suffix ING, the part of speech is specified as VERBING, while ED
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indicates that the part-of-speech set is (VERBEN, VERB (SING TR) (PL TR)). If
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the last morph is S or ES, a number of checks must be made. If the next to last
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morph is not a suffix and there is a verb-producing prefix, then the part of speech
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is VERB (SING TR), as in entitles. If the penultimate morph has the part of
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speech VERB, then the same part of speech is assigned. If the previous morph is a
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NOUN, ADJ, or INTG or is ER or ING, then the part of speech NOUN (NUM
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PL) is added to the set. If the next to last morph is an ORD, then the part of speech
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is also ORD (NUM PL). Finally, if there is still no part of speech, the processor
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assigns NOUN (NUM PL), as in the whys and wherefores.
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If the last suffix is ER, then three checks are made. If the next to last morph
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has the part of speech ADV, then the word is a comparative adverb; if it is an AD]J,
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then the word is a comparative adjective. If it is a NOUN or a VERB, then the
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word is a singular NOUN, as in worker. If the last morph is S’, then the word’s
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part of speech is NOUN with the property (POSS TR).
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