public abstract class RSLPStemmerBase extends Object
RSLP (Removedor de Sufixos da Lingua Portuguesa) is an algorithm designed originally for stemming the Portuguese language, described in the paper A Stemming Algorithm for the Portuguese Language, Orengo et. al.
Since this time a plural-only modification (RSLP-S) as well as a modification
for the Galician language have been implemented. This class parses a configuration
file that describes RSLPStemmerBase.Step
s, where each Step contains a set of RSLPStemmerBase.Rule
s.
The general rule format is:
{ "suffix", N, "replacement", { "exception1", "exception2", ...}}where:
suffix
is the suffix to be removed (such as "inho").
N
is the min stem size, where stem is defined as the candidate stem
after removing the suffix (but before appending the replacement!)
replacement
is an optimal string to append after removing the suffix.
This can be the empty string.
exceptions
is an optional list of exceptions, patterns that should
not be stemmed. These patterns can be specified as whole word or suffix (ends-with)
patterns, depending upon the exceptions format flag in the step header.
A step is an ordered list of rules, with a structure in this format:
{ "name", N, B, { "cond1", "cond2", ... } ... rules ... };where:
name
is a name for the step (such as "Plural").
N
is the min word size. Words that are less than this length bypass
the step completely, as an optimization. Note: N can be zero, in this case this
implementation will automatically calculate the appropriate value from the underlying
rules.
B
is a "boolean" flag specifying how exceptions in the rules are matched.
A value of 1 indicates whole-word pattern matching, a value of 0 indicates that
exceptions are actually suffixes and should be matched with ends-with.
conds
are an optional list of conditions to enter the step at all. If
the list is non-empty, then a word must end with one of these conditions or it will
bypass the step completely as an optimization.
Modifier and Type | Class and Description |
---|---|
protected static class |
RSLPStemmerBase.Rule
A basic rule, with no exceptions.
|
protected static class |
RSLPStemmerBase.RuleWithSetExceptions
A rule with a set of whole-word exceptions.
|
protected static class |
RSLPStemmerBase.RuleWithSuffixExceptions
A rule with a set of exceptional suffixes.
|
protected static class |
RSLPStemmerBase.Step
A step containing a list of rules.
|
Constructor and Description |
---|
RSLPStemmerBase() |
Modifier and Type | Method and Description |
---|---|
protected static Map<String,RSLPStemmerBase.Step> |
parse(Class<? extends RSLPStemmerBase> clazz,
String resource)
Parse a resource file into an RSLP stemmer description.
|
protected static Map<String,RSLPStemmerBase.Step> parse(Class<? extends RSLPStemmerBase> clazz, String resource)
Copyright © 2000-2017 Apache Software Foundation. All Rights Reserved.