--- /dev/null
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+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+<html>
+<head></head>
+<body>
+The calculus of spans.
+
+<p>A span is a <code><doc,startPosition,endPosition></code> tuple.</p>
+
+<p>The following span query operators are implemented:
+
+<ul>
+
+<li>A <a href="SpanTermQuery.html">SpanTermQuery</a> matches all spans
+containing a particular <a href="../../index/Term.html">Term</a>.</li>
+
+<li> A <a href="SpanNearQuery.html">SpanNearQuery</a> matches spans
+which occur near one another, and can be used to implement things like
+phrase search (when constructed from <a
+href="SpanTermQuery.html">SpanTermQueries</a>) and inter-phrase
+proximity (when constructed from other <a
+href="SpanNearQuery.html">SpanNearQueries</a>).</li>
+
+<li>A <a href="SpanOrQuery.html">SpanOrQuery</a> merges spans from a
+number of other <a href="SpanQuery.html">SpanQueries</a>.</li>
+
+<li>A <a href="SpanNotQuery.html">SpanNotQuery</a> removes spans
+matching one <a href="SpanQuery.html">SpanQuery</a> which overlap
+another. This can be used, e.g., to implement within-paragraph
+search.</li>
+
+<li>A <a href="SpanFirstQuery.html">SpanFirstQuery</a> matches spans
+matching <code>q</code> whose end position is less than
+<code>n</code>. This can be used to constrain matches to the first
+part of the document.</li>
+
+</ul>
+
+In all cases, output spans are minimally inclusive. In other words, a
+span formed by matching a span in x and y starts at the lesser of the
+two starts and ends at the greater of the two ends.
+</p>
+
+<p>For example, a span query which matches "John Kerry" within ten
+words of "George Bush" within the first 100 words of the document
+could be constructed with:
+<pre class="prettyprint">
+SpanQuery john = new SpanTermQuery(new Term("content", "john"));
+SpanQuery kerry = new SpanTermQuery(new Term("content", "kerry"));
+SpanQuery george = new SpanTermQuery(new Term("content", "george"));
+SpanQuery bush = new SpanTermQuery(new Term("content", "bush"));
+
+SpanQuery johnKerry =
+ new SpanNearQuery(new SpanQuery[] {john, kerry}, 0, true);
+
+SpanQuery georgeBush =
+ new SpanNearQuery(new SpanQuery[] {george, bush}, 0, true);
+
+SpanQuery johnKerryNearGeorgeBush =
+ new SpanNearQuery(new SpanQuery[] {johnKerry, georgeBush}, 10, false);
+
+SpanQuery johnKerryNearGeorgeBushAtStart =
+ new SpanFirstQuery(johnKerryNearGeorgeBush, 100);
+</pre>
+
+<p>Span queries may be freely intermixed with other Lucene queries.
+So, for example, the above query can be restricted to documents which
+also use the word "iraq" with:
+
+<pre class="prettyprint">
+Query query = new BooleanQuery();
+query.add(johnKerryNearGeorgeBushAtStart, true, false);
+query.add(new TermQuery("content", "iraq"), true, false);
+</pre>
+
+</body>
+</html>
fnp / pylucene.git / blobdiff