Hermit Crab Parsing Engine Specification
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- 4Results of Morpher Application
- 4.1.1Definition of Translation between String and Phonetic Sequence
- 4.1.1.1Translation from String to Phonetic Sequence
- 4.1.1.2Translation from Phonetic Sequence to a Regular Expression
- 4.1.2Definition of the Partition of a Phonetic Sequence by a Phonetic Template
3.6Analyzable WordAn input word is analyzable if it can be matched by the morpher with one or more complete lexical entries. An input token (word) matches a complete lexical entry if the phonetic shape of the complete lexical entry is identical to the input token's shape. 4Results of Morpher ApplicationThis section defines the application of morphological and phonological rules to lexical entries. 4.1Phonetic RepresentationExternally, there are two different representations for sequences of phonetic segments in the morpher. Input words (tokens) and the phonetic shape of Real Lexical Entries are represented as strings, in which each segment and/or suprasegmental is represented by one or more string characters. Phonological and morphological rules, on the other hand, use a Phonetic Template data structure (defined below), in which each segment is defined in terms of its phonetic features. These differing representations are made compatible internally to the morpher by being translated into a Phonetic Sequence (also defined below). At the other “end”, the phonetic shape of a virtual lexical entry (i.e. a lexical entry derived by the application of phonological and/or morphological rules) is translated from a Phonetic Sequence into a string before lexical lookup. We therefore begin with definitions of the correspondences among these phonetic representations: strings of characters, phonetic templates, and phonetic sequences. 4.1.1Definition of Translation between String and Phonetic SequenceThe translation between a string and its representation as a Phonetic Sequence makes use of the Character Definition Table (defined below). The translation from string to phonetic sequence is unambiguous; the reverse translation may be ambiguous. The translations are defined here in algorithmic form for convenience. (Hermit Crab need not use the same algorithm internally.) 4.1.1.1Translation from String to Phonetic SequenceThe translation of the string representing an input word into a phonetic sequence, defined in this section, is unambiguous. The phrase “exit with error, returning X” means return an error message containing X. Error messages for this translation process are listed under the command morph_and_lookup_word. Let Str be a string consisting of string characters C1...Cm. (String characters are defined in chapter two.) This string may be translated into the Phonetic Sequence PS = (F1...Fn), where each Fi is a boundary marker or a set of phonetic features by the following procedure. (1) Set PS equal to the empty list. (2) Remove from Str the longest sequence of characters C = C1..Cj beginning at the left of Str and matching a Character Sequence in the Character Definition Table. (Note that Str is now of length m–j.) If no sequence beginning at the left end of Str matches with any Character Sequence in the Character Definition Table, exit with failure, returning the first character of Str. (3) If sequence C matches the Character Sequence of a Segment Definition Record, append the Phonetic Features field of that Segment Definition Record to the right end of PS. If sequence C matches the Character Sequence of a Boundary Definition Record, append C to the right end of PS. (Boundary markers are not associated with any phonetic features, hence the character(s) which represent them in Str are also used to represent them in PS.) (4) If Str is non-empty, go to step (2). Else exit with success, returning PS. Note that some features in PS may be uninstantiated for some segments. 4.1.1.2Translation from Phonetic Sequence to a Regular ExpressionIn the following definition of the translation from phonetic sequence to a regular expression, no translation is defined for a Phonetic Sequence which contains an Optional Segment Sequence record. Phonetic sequences containing Optional Segment Sequence records should appear only in rule environments, not in the structural change of rules or in lexical entries, and therefore will never need to be translated into a regular expression. (However, traces of rule unapplication may contain optional segments resulting from the unapplication of epenthesis or deletion rules (see section 5.8.3.2 Phonological Rule Analysis Trace Record--Rule Input.) Let PS = (F1..Fn) be a Phonetic Sequence. This list may be translated into the Regular Expression RegExpr consisting of the terms C1..Cm by the following algorithm. (If each Fi is sufficiently instantiated to be unambiguously translated into a segment, RegExpr will represent a single string.) (1) Set RegExpr equal to the empty string, and i = 1. (2) (a) If Fi is a string (i.e. a boundary marker), append it to the right end of RegExpr (bracketing it with ASCII 2 (STX) and ASCII 3 (ETX) to the left and right respectively if it is marked “optional”), and go to step (3). (b) Else, let SDR = {SDRi...SDRj} be the set of all Segment Definition Records whose Phonetic Features Field are a superset of Fi, and let CS = {CS1...CSj} be the set of Character Sequences of SDRi. Then if SDR is of length one (i.e. Fi is unambiguously translatable into a segment), set RegExpr equal to the result of appending CS1 to the right end of RegExpr; else (if SDR is of length greater than one, meaning Fi is ambiguously translatable), set RegExpr equal to RegExpr plus an ASCII 28 (FS) plus the members of CS, each separated by an ASCII 29 (GS), plus an ASCII 30 (RS). If the segment(s) is/are marked as optional, enclose the segment or the bracketed list of segments in ASCII 2 (STX) and ASCII 3 (ETX) to the left an right respectively. If there is no Segment Definition Record whose features are a superset of Fi, exit with error, returning Fi. (3) If i < n, set i = i+1 and go to step 2. Else exit with success, returning RegExpr. 4.1.2Definition of the Partition of a Phonetic Sequence by a Phonetic TemplateLet PSTSeq = (PST1...PSTm) be a Phonetic Sequence of a Phonetic Template, and let INIT and FINAL be the values of the init and final fields of that Phonetic Template. Furthermore, let PSLSeq = (PSLx...PSLy) (the Lexical Sequence) be a subsequence of the Phonetic Sequence PSL1...PSLz of a lexical entry. Then PSTSeq partitions PSLSeq into the list PART = (BMs1 Part1...BMSm Partm BMsm+1), where each MSsi is a list of zero or more Boundary Markers, and Parti is a variable-free phonetic sequence, iff: (1) If INIT is true, the left-most segment of the left-most non-empty Parti in PART is PSL1 (i.e. PSTSeq must match PSLSeq beginning at the left-most segment of PSLSeq); (2) If FINAL is true, the right-most segment of the right-most non-empty Parti in PART is PSLy (i.e. PSTSeq must match PSLSeq ending with the right-most segment of PSLSeq); (3) If PSTi is a Simple Context, then Parti contains a single segment Seg such that PSTi is a subset of Seg (i.e. every feature in PSTi has that same value in Seg); (4) If PSTi is a string of one or more boundary markers, then Parti is that same string of boundary markers; (5) If PSTi is an Optional Segment Sequence, let MIN and MAX be the values of the Minimum Occurrence and Maximum Occurrence fields of PSTi (default 0 and 1, respectively), and let PSTSeq be the Optional Sequence of PSTi. Then Parti is a list divisible into between MIN and MAX nonoverlapping adjacent subsequences, each of which matches PSTi; and (6) For all i, BMi is a list of zero or more boundary markers. (Boundary markers in the lexical sequence need not be accounted for by the template; this corresponds to the generally accepted notion that phonological rules can apply freely across morpheme boundaries. However, the definition of the application of a phonetic rule to a lexical entry, as given below, requires that the portion of a phonetic sequence matched by the input of a phonetic rule must not contain a boundary marker unless the marker is specifically required by the rule.)
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