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SynExpand.javaAPI DocApache Lucene 2.2.05017Sat Jun 16 22:20:46 BST 2007org.apache.lucene.wordnet

SynExpand

public final class SynExpand extends Object
Expand a query by looking up synonyms for every term. You need to invoke {@link Syns2Index} first to build the synonym index.
see
Syns2Index

Fields Summary
Constructors Summary
Methods Summary
public static org.apache.lucene.search.Queryexpand(java.lang.String query, org.apache.lucene.search.Searcher syns, org.apache.lucene.analysis.Analyzer a, java.lang.String field, float boost)
Perform synonym expansion on a query.

param
query users query that is assumed to not have any "special" query syntax, thus it should be just normal words, so "big dog" makes sense, but a query like "title:foo^1.2" doesn't as this should presumably be passed directly to the default query parser.
param
syns a opened to the Lucene index you previously created with {@link Syns2Index}. The searcher is not closed or otherwise altered.
param
a optional analyzer used to parse the users query else {@link StandardAnalyzer} is used
param
field optional field name to search in or null if you want the default of "contents"
param
boost optional boost applied to synonyms else no boost is applied
return
the expanded Query

		Set already = new HashSet(); // avoid dups 
		List top = new LinkedList(); // needs to be separately listed..
		if ( field == null) field = "contents";
		if ( a == null) a = new StandardAnalyzer();

		// [1] Parse query into separate words so that when we expand we can avoid dups
		TokenStream ts = a.tokenStream( field, new StringReader( query));
		org.apache.lucene.analysis.Token t;
		while ( (t = ts.next()) != null)
		{
			String word = t.termText();
			if ( already.add( word))
				top.add( word);
		}
		BooleanQuery tmp = new BooleanQuery();
		
		// [2] form query
		Iterator it = top.iterator();
		while ( it.hasNext())
		{
			// [2a] add to level words in
			String word = (String) it.next();
			TermQuery tq = new TermQuery( new Term( field, word));
			tmp.add( tq, BooleanClause.Occur.SHOULD);

			// [2b] add in unique synonums
			Hits hits = syns.search( new TermQuery( new Term(Syns2Index.F_WORD, word)));
			for (int i = 0; i < hits.length(); i++)
			{
				Document doc = hits.doc(i);
				String[] values = doc.getValues( Syns2Index.F_SYN);
				for ( int j = 0; j < values.length; j++)
				{
					String syn = values[ j];
					if ( already.add( syn)) // avoid dups of top level words and synonyms
					{
						tq = new TermQuery( new Term( field, syn));
						if ( boost > 0) // else keep normal 1.0
							tq.setBoost( boost);
						tmp.add( tq, BooleanClause.Occur.SHOULD); 
					}
				}
			}
		}


		return tmp;
public static voidmain(java.lang.String[] args)
Test driver for synonym expansion. Uses boost factor of 0.9 for illustrative purposes. If you pass in the query "big dog" then it prints out: 
Query: big adult^0.9 bad^0.9 bighearted^0.9 boastful^0.9 boastfully^0.9 bounteous^0.9 bountiful^0.9 braggy^0.9 crowing^0.9 freehanded^0.9 giving^0.9 grown^0.9 grownup^0.9 handsome^0.9 large^0.9 liberal^0.9 magnanimous^0.9 momentous^0.9 openhanded^0.9 prominent^0.9 swelled^0.9 vainglorious^0.9 vauntingly^0.9
dog andiron^0.9 blackguard^0.9 bounder^0.9 cad^0.9 chase^0.9 click^0.9 detent^0.9 dogtooth^0.9 firedog^0.9 frank^0.9 frankfurter^0.9 frump^0.9 heel^0.9 hotdog^0.9 hound^0.9 pawl^0.9 tag^0.9 tail^0.9 track^0.9 trail^0.9 weenie^0.9 wiener^0.9 wienerwurst^0.9


		if (args.length != 2)
		{
			System.out.println(
							   "java org.apache.lucene.wordnet.SynExpand <index path> <query>");
		}

		FSDirectory directory = FSDirectory.getDirectory(args[0], false);
		IndexSearcher searcher = new IndexSearcher(directory);

		String query = args[1];
		String field = "contents";

		Query q = expand( query, searcher, new StandardAnalyzer(), field, 0.9f);
		System.out.println( "Query: " + q.toString( field));



		searcher.close();
		directory.close();