NAME
Lingua::Phonology::Symbols - a module for associating symbols with segment prototypes.
SYNOPSIS
use Lingua::Phonology;
$phono = new Lingua::Phonology;
# Load the default features
$phono->features->loadfile;
# Load the default symbols
$symbols = $phono->symbols;
$symbols->loadfile;
# Make a test segment
$segment = $phono->segment;
$segment->labial(1);
$segment->voice(1);
# Find the symbol matching the segment
print $symbols->spell($segment); # Should print 'b'DESCRIPTION
When using Lingua::Phonology, you usually manipulate Segment objects that have various feature values that specify the phonetic qualities of the segment. However, it is difficult to print those feature values, and a list of feature values can be difficult to interpret anyway. This is where Symbols comes in--it provides a way to take a Segment object and get a phonetic symbol representing the properties of that segment.
In Symbols, you may use symbol() to define text symbols that correlate to "prototypes", which are special Segment objects that represent the ideal segment for each symbol. After you have defined your symbols and prototypes, you may use spell() to find which prototype is the most similar to a segment in question, and get the symbol for that prototype.
As of v0.2, Symbols also includes diacritics. A diacritic is a special symbol that begins or ends with a '*', and which is used to modify other symbols. If the best symbol match for a segment you are trying to spell is an imperfect match, Symbols will then attempt to use diacritics to indicate exactly how the segment is pronounced. For compatibility reasons, however, this feature is off by default. It can be turned on with set_diacritics.
You will probably want to read the symbol, spell, and loadfile sections, because these describe the most widely-used functions and the algorithm used to score potential matches. If you're not getting the results you expect, you probably need to examine the way your prototype definitions are interacting with that algorithm.
INDEXING
This section endeavors to explain the purpose of indexing in Lingua::Phonology::Symbols, and how you can control it.
As of v0.2, this module uses an efficient hash comparison algorithm that greatly speeds up calls to spell and score. This algorithm works by compiling an index of the features and values that prototype segments have, then only comparing against those prototypes that have some chance of winning. Indexing itself is a somewhat costly procedure, but fortunately, it only needs to be done once. Unfortunately, it needs to be done again any time that the list of symbols or the prototypes for those symbols is changed.
Fortunately again, Lingua::Phonology::Symbols will take care of this for you. Whenever a method is called that might require reindexing, an internal flag on the object will be set. The next time that you ask this module to spell something, it will first reindex, then proceed to spelling. The methods that will trigger reindexing are symbol, drop_symbol, change_symbol, loadfile, prototype. This reindexing is done "just in time", and isn't done more than is necessary.
Unfortunately, not all calls to those methods actually warrant reindexing, so if you call those methods a lot, you might want to have manual control over when the hash is reindexed. To do this, you can use the method no_auto_reindex, which will disable automatic reindexing. You then will have to call reindex yourself whenever it's warranted. If you get tired of this and want reindexing back, you can call set_auto_reindex.
The author of this module has never felt the need to work with auto reindexing off, for what it's worth.
METHODS
new
Creates a new Symbols object. This method takes one argument, a Features object that provides the feature set for the prototypes in this object. This will carp if you don't provide an appropriate object.
This method is called automatically when you make a new Lingua::Phonology.
symbol
Adds one or more symbols to the current object. The argument to symbol must be a hash. The keys of this hash are the text symbols that will be returned, and the values should be Segment objects that act as the prototypes for each symbol. See "spell" for explanation of how these symbols and protoypes are used.
Symbols can generally be any text string. However, strings beginning or ending with '*' are interpreted specially, as diacritics. The position of the asterisk indicates where the base symbol goes, and the rest is interpreted as the diacritic. Diacritic prototypes are also treated differently from regular prototypes--see the spell section for details. For example, you could use a tilde '~' following a symbol to indicate nasality with the following call to symbol:
# Assume $nasal is an appropriate prototye
$symbols->symbol('*~' => $nasal);Note that '*' by itself is still a valid, non-diacritic symbol. However, '**' will be interpreted as a diacritic consisting of a symbol followed by a single asterisk.
If you attempt to pass in a Segment object associated with a feature set other than the one defined for the current object, symbol() will skip to the next symbol and emit a warning, if warnings are turned on.
This method returns true if all of the attempted symbol additions succeeded, and false otherwise.
drop_symbol
Deletes a symbol from the current object. Nothing happens if you try to delete a symbol which doesn't currently exist.
change_symbol
Acts exactly the same as symbol(), but first checks to make sure that there already exists a symbol with the key given. Otherwise, it brings up an error.
The method symbol() can also be used to redefine existing symbols; this method is provided only to aid readability.
As with symbol(), this method returns true if all of the attempted changes succeeded, otherwise false.
reindex
This function recompiles the internal index that Lingua::Phonology::Symbols uses to speed up spelling. It should generally be unnecessary to call this function, as Lingua::Phonology::Symbols does its best to figure out when reindexing is necessary without any user input. You may call this function by hand to ensure reindexing at a particular time, or if auto reindexing is off.
auto_reindex
Returns true if automatic reindexing is currently turned on, false otherwise. If called with an argument, sets auto reindexing to the truth or falsehood of that argument. Auto reindexing is on by default.
set_auto_reindex
Turns automatic reindexing (back) on. Same as auto_reindex(1). Auto reindexing is on by default, so this is only necessary after a call to no_auto_reindex. See INDEXING.
no_auto_reindex
Turns automatic reindexing off. Same as auto_reindex(0). See INDEXING.
diacritics
Returns true if diacritics are currently on, otherwise false. You may also pass this method an argument to turn diacritics on or off, e.g. $symbols->diacritics(1). Diacritics are off by default.
set_diacritics
Turns diacritics on. Same as diacritics(1).
no_diacritics
Turns diacritics off. Same as diacritics(0).
loadfile
Takes one argument, a file name, and loads prototype segment definitions from that file. If no file name is given, loads the default symbol set.
Lines in the file should match the regular expression /^\s*(\S+)\t+(.*)/. The first parenthesized sub-expression will be taken as the symbol, and the second sub-expression as the feature definitions for the prototype. Feature definitions are separated by spaces, and should be in one of three formats:
feature: The preferred way to set a privative value is simply to write the name of the feature unadorned. Since privatives are either true or undef, this is sufficient to declare the existence of a privative. E.g., since both [labial] and [voice] are privatives in the default feature set, the following line suffices to define the symbol 'b' (though you may want more specificity):
b labial voice[+-*]feature: The characters before the feature correspond to setting the value to true, false, and undef, respectively. This is the preferred way to set binary features, and the only way to assert that a feature of any type must be undef. For example, the symbol 'd`' for a voiced retroflex stop can be defined with the following line:
d` -anterior -distributed voicefeature=value: Whatever precedes the equals sign is the feature name; whatever follows is the value. This is the preferred way to set scalar values, and the only way to set scalar values to anything other than undef, 0, or 1.
Feature definitions may work if you use them other than as recommended, but the recommended forms are provided for maximum readability. To be exact, however, the following are synonymous:
# Synonymous one way
labial
+labial
labial=1
# Synonymous in a different way
-labial # only if 'labial' is binary
labial=0Since this behavior is partly dependent on the implementation of text and number forms in the Features module, the synonymity of these forms is not guaranteed to remain constant in the future. However, every effort will be made the guarantee that the recommended forms won't change their behavior.
You may begin comments with '#'--anything between the first '#' on a line and the end of that line will be ignored. Consequently, '#' cannot be used as a symbol in a loaded file (though it is a valid symbol elsewhere, and can be assigned via symbol()).
As with symbol(), symbol definitions beginning or ending with '*' will be interpreted as diacritics. Diacritic symbols may be defined in exactly the same way as regular symbols. Thus, to define a tilde as a diacritic for nasality, you might use the following simple line:
*~ nasalYou should only define terminal (non-node) features in your segment definitions. The loadfile method is unable to deal with features that are nodes, and will generate errors if you try to assign to a node.
If you don't give a file name, then the default symbol set is loaded. This is described in "THE DEFAULT SYMBOL SET".
spell
Takes any number of Segment objects as arguments. For each object, returns a text string indicating the best match of prototype with the Segment given. In a scalar context, returns a string consisting of a concatencation of all of the symbols.
The Symbol object given will be compared against every prototype currently defined, and scored according to the following algorithm:
Score one point for every feature that is defined for both the prototype and the comparison segment, and for which the values for those features agree.
Lose one point for every feature that is defined for the prototype but is not defined for the comparison segment.
Lose two points for every feature that is defined for both the prototype and the comparison segment, but for which the values do not agree.
Comparison segments may always be more defined than the prototypes, so there is no consequence if the comparison segment is defined for features that the prototype isn't defined for.
The 'winning' prototype is the one that scores the highest by the preceding algorithm. If more than one prototype scores the same, it's unpredictable which symbol will be returned, since it will depend on the order in which the prototypes came out of the internal hash.
If diacritics is on, diacritic formation happens after the best-matching symbol is chosen. A list of the features for which the comparison segment and symbol prototypes do not agreeis compiled, and diacritics are selected that match against those features. If there are diacritics that specify more than one feature, or multiple diacritics specifying the same feature, then this method will attempt to minimize the number of diacritics used. The diacritic symbols will be concatenated with the base symbol, the base symbol taking the place of the asterisk in the symbol definition. For example, if a segment matched the base symbol 'a' and the diacritic '*~', the resulting symbol would be 'a~'. If multiple diacritics are matched, there is no way to predict the order in which they will be added.
If no prototype scores at least 1 point by this algorithm, the string '_?_' will be returned. This indicates that no suitable matches were found. No diacritic matching is done in this case.
Beware of testing a Segment object that is associated with a different feature set than the ones used by the prototypes. This will almost certainly cause errors and bizarre results.
Note that spell() is fairly expensive (though it's a lot quicker than it used to be).
score
Takes a Segment argument and compares it against the defined symbols, just like symbol(). It normally returns a hash with the available symbols as the keys and the score for each symbol as the value. In a scalar context, returns the winning symbol just like spell(). Useful for debugging and determining why the program thinks that [a] is better described as [d] (as happened to the author during testing). Unfortunately, score() can only be used to test one segment at a time, rather than a list of segments.
The hash returned from score() may at times contain keys whose values are 0 where they "shouldn't" be. This is because score() uses a lazy algorithm that stops evaluating once a symbol's score has reached 0 and it cannot go up. Thus, many symbols will show a score of zero when their score would actually be negative if evaluation were carried to its conclusion.
prototype
Takes one argument, a text string indicating a symbol in the current set. Returns the prototype associated with that symbol, or carps if no such symbol is defined. You can then make changes to the prototype object, which will be reflected in subsequent calls to spell().
segment
Takes one or more argument, a symbol, and return a new Segment object with the feature values of the prototype for that symbol. Unlike prototype, which return the prototype itself, this method returns a completely new object which can be modified without affecting the values of the prototype. If you supply a list of symbols, you'll get back a list of segments in the same order. This is generally the easiest way to make new segments with some features already set. Example:
# One segment at a time
$b = $symbols->segment('b');
# Many at a time
@word = $symbols->segment('b', 'a', 'n');The segments returned from this method will already be associated with the current Lingua::Phonology::Features object and the current Symbols object.
features
Returns the Features object associated with the current object, or sets the object if provided with a Lingua::Phonology::Features object as an argument.
THE DEFAULT SYMBOL SET
Currently, Lingua::Phonology::Symbols comes with a set of symbols that can be loaded by calling loadfile with no arguments, like so:
$symbols->loadfile;The symbol set thus loaded is based on the X-SAMPA system for encoding the IPA into ASCII. You can read more about X-SAMPA at http://www.phon.ucl.ac.uk/home/sampa/x-sampa.htm. The default does not contain all of the symbols in X-SAMPA, but it does contain a lot of them. The symbols defined are as follows.
# Symbol definitions
# Labial
p labial -continuant
b labial voice -continuant
f labial +continuant
v labial voice +continuant
m labial sonorant nasal -continuant
# Dental and alveolar
t +anterior -continuant
d +anterior voice -continuant
s +anterior -distributed +continuant
z +anterior -distributed voice +continuant
T +anterior +distributed +continuant
D +anterior +distributed voice +continuant
n +anterior sonorant nasal -continuant
l +anterior sonorant lateral approximant
r +anterior sonorant approximant
# Palato-alveolar
tS -anterior +distributed -continuant
dZ -anterior +distributed voice -continuant
S -anterior +distributed +continuant
Z -anterior +distributed +continuant voice
# Retroflex
t` -anterior -distributed -continuant
d` -anterior -distributed voice -continuant
s` -anterior -distributed +continuant
z` -anterior -distributed +continuant voice
n` -anterior -distributed sonorant nasal -continuant
l` -anterior -distributed sonorant lateral approximant
r` -anterior -distributed sonorant approximant
# Palatal
c -anterior dorsal -continuant
d\ -anterior dorsal -continuant voice
C -anterior dorsal +continuant
j\ -anterior dorsal +continuant voice
J -anterior dorsal -continuant sonorant nasal
L -anterior dorsal sonorant lateral approximant
# Velar
k dorsal -continuant
g dorsal voice -continuant
x dorsal +continuant
G dorsal voice +continuant
N dorsal sonorant nasal -continuant
# Uvular
q dorsal pharyngeal -continuant
G\ dorsal pharyngeal -continuant voice
X dorsal pharyngeal +continuant
R dorsal pharyngeal +continuant voice
N\ dorsal pharyngeal sonorant nasal -continuant
R\ dorsal pharyngeal sonorant approximant
# Pharyngeal
q\ pharyngeal -continuant
X\ pharyngeal +continuant
?\ pharyngeal +continuant voice
# Glottal
? -continuant
h +continuant
h\ +continuant voice
# Vowels and vocoids
# High vowels
i vocoid approximant sonorant aperture=0 -anterior tense
j vocoid approximant sonorant aperture=0 -anterior tense *nucleus
I vocoid approximant sonorant aperture=0 -anterior
u vocoid approximant sonorant aperture=0 dorsal labial tense
w vocoid approximant sonorant aperture=0 dorsal labial tense *nucleus
U vocoid approximant sonorant aperture=0 dorsal labial
y vocoid approximant sonorant aperture=0 -anterior labial tense
Y vocoid approximant sonorant aperture=0 -anterior labial
M vocoid approximant sonorant aperture=0 dorsal labial
1 vocoid approximant sonorant aperture=0
} vocoid approximant sonorant aperture=0 labial
# Mid vowels
e vocoid approximant sonorant aperture=1 -anterior tense
E vocoid approximant sonorant aperture=1 -anterior
o vocoid approximant sonorant aperture=1 dorsal labial tense
O vocoid approximant sonorant aperture=1 dorsal labial
V vocoid approximant sonorant aperture=1 dorsal
2 vocoid approximant sonorant aperture=1 -anterior labial tense
9 vocoid approximant sonorant aperture=1 -anterior labial
@ vocoid approximant sonorant aperture=1
8 vocoid approximant sonorant aperture=1 labial
# Low vowels
a vocoid approximant sonorant aperture=2
Q vocoid approximant sonorant aperture=2 labial
# Diacritics
*_0 *voice
*_v voice
*_h spread
*_~ constricted
*_w labial
*_G dorsal
*_?\ pharyngeal
*_d +distributed # Diacritic for "dental"
*~ nasal
*_l lateralThese symbols depend upon the default feature set. If you aren't using the default feature set, you're on your own. If you've modified the default feature set, these may still work, though you'll probably have to tweak them. YMMV.
TO DO
Expand the default symbols set.
Add functionality for diacritics to modify imperfect matches.
SEE ALSO
Lingua::Phonology, Lingua::Phonology::Features
AUTHOR
Jesse S. Bangs <jaspax@u.washington.edu>.
LICENSE
This module is free software. You can distribute and/or modify it under the same terms as Perl itself.