org.apache.lucene.analysis.pt

## Class RSLPStemmerBase

- java.lang.Object
- - org.apache.lucene.analysis.pt.RSLPStemmerBase

Direct Known Subclasses:
  GalicianMinimalStemmer, GalicianStemmer, PortugueseMinimalStemmer, PortugueseStemmer

    public abstract class RSLPStemmerBase
    extends Object

Base class for stemmers that use a set of RSLP-like stemming steps.

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.

See Also:
  RSLP description
NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

### Nested Class Summary

Nested Classes
`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 Summary

Constructors
Constructor and Description
`RSLPStemmerBase()`

### Method Summary

All Methods Static Methods Concrete Methods
`protected static Map<String,RSLPStemmerBase.Step>` `parse(Class<? extends RSLPStemmerBase> clazz, String resource)` Parse a resource file into an RSLP stemmer description.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Constructor Detail

#### RSLPStemmerBase

    public RSLPStemmerBase()

### Method Detail

#### parse

    protected static Map<String,RSLPStemmerBase.Step> parse(Class<? extends RSLPStemmerBase> clazz,
                                                            String resource)

Parse a resource file into an RSLP stemmer description.

Returns:
  a Map containing the named Steps in this description.