it.unimi.di.mg4j.query.nodes
Class AbstractTermExpander

java.lang.Object
  it.unimi.di.mg4j.query.nodes.AbstractTermExpander

All Implemented Interfaces:

QueryTransformer

Direct Known Subclasses:

MultiIndexTermExpander

public abstract class AbstractTermExpander
extends Object
implements QueryTransformer

A query transformer that just requires implementing a method that expands terms (e.g., into disjunctive queries).

To implement more sophisticated behaviours, you can subclass the internal class AbstractTermExpander.ExpanderVisitor, and override the method expanderVisitor() so that it returns a (possibly cached) instance of your own visitor class (see, for an example, MultiIndexTermExpander).

Nested Class Summary

protected class

AbstractTermExpander.ExpanderVisitor

Constructor Summary

AbstractTermExpander()

Method Summary

abstract Query	expand(Prefix prefix) Expands a prefix.
abstract Query	expand(Term term) Expands a single term.
protected AbstractTermExpander.ExpanderVisitor	expanderVisitor() Returns a new expander visitor.
Query	transform(Query query)

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractTermExpander

public AbstractTermExpander()

Method Detail

expanderVisitor

protected AbstractTermExpander.ExpanderVisitor expanderVisitor()

Returns a new expander visitor.

Returns:

a visitor performing the expansion.

transform

public Query transform(Query query)

Specified by:

transform in interface QueryTransformer

expand

public abstract Query expand(Term term)

Expands a single term.

Parameters:

term - a term to be expanded.

Returns:

the resulting query.

expand

public abstract Query expand(Prefix prefix)

Expands a prefix.

Parameters:

prefix - the prefix to be expanded.

Returns:

the resulting query.