Index: analysis/common/src/java/org/apache/lucene/analysis/miscellaneous/ScandinavianFoldingFilter.java
===================================================================
--- analysis/common/src/java/org/apache/lucene/analysis/miscellaneous/ScandinavianFoldingFilter.java	(revision 0)
+++ analysis/common/src/java/org/apache/lucene/analysis/miscellaneous/ScandinavianFoldingFilter.java	(arbetskopia)
@@ -0,0 +1,134 @@
+package org.apache.lucene.analysis.miscellaneous;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (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.
+ */
+
+import org.apache.lucene.analysis.TokenFilter;
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
+import org.apache.lucene.analysis.util.StemmerUtil;
+
+import java.io.IOException;
+
+
+/**
+ * This filter folds Scandinavian characters åäæÅÄÆ->a and öøÖØ->o.
+ * It also discriminate against use of double vowels aa, ae, ao, oe and oo, leaving just the first one.
+ * <p/>
+ * blåbærsyltetøj == blåbärsyltetöj == blaabaarsyltetoej == blabarsyltetoj
+ * räksmörgås == ræksmørgås == ræksmörgaos == raeksmoergaas == raksmorgas
+ * <p/>
+ * Background:
+ * Swedish åäö are in fact the same letters as Norwegian and Danish åæø and thus interchangeable
+ * when used between these languages. They are however folded differently when people type
+ * them on a keyboard lacking these characters.
+ * <p/>
+ * When a Swedish person is lacking umlauted characters on the keyboard
+ * they consistently type a, a, o instead of å, ä, ö. Foreigners also tend to use a, a, o.
+ * <p/>
+ * In Norway people tend to type aa, ae and oe instead of å, æ and ø.
+ * Some use a, a, o. I've also seen oo, ao, etc. And permutations.
+ * Not sure about Denmark but the pattern is probably the same.
+ * <p/>
+ * This filter solves that problem, but might also cause new.
+ */
+public class ScandinavianFoldingFilter extends TokenFilter {
+
+  public ScandinavianFoldingFilter(TokenStream input) {
+    super(input);
+  }
+
+  private final CharTermAttribute charTermAttribute = addAttribute(CharTermAttribute.class);
+
+  private static final char AA = '\u00C5'; // Å
+  private static final char aa = '\u00E5'; // å
+  private static final char AE = '\u00C6'; // Æ
+  private static final char ae = '\u00E6'; // æ
+  private static final char AE_se = '\u00C4'; // Ä
+  private static final char ae_se = '\u00E4'; // ä
+  private static final char OE = '\u00D8'; // Ø
+  private static final char oe = '\u00F8'; // ø
+  private static final char OE_se = '\u00D6'; // Ö
+  private static final char oe_se = '\u00F6'; //ö
+
+
+  @Override
+  public boolean incrementToken() throws IOException {
+    if (!input.incrementToken()) {
+      return false;
+    }
+
+    char[] buffer = charTermAttribute.buffer();
+    int length = charTermAttribute.length();
+
+
+    int i;
+    for (i = 0; i < length; i++) {
+
+      if (buffer[i] == aa
+          || buffer[i] == ae_se
+          || buffer[i] == ae) {
+
+        buffer[i] = 'a';
+
+      } else if (buffer[i] == AA
+          || buffer[i] == AE_se
+          || buffer[i] == AE) {
+
+        buffer[i] = 'A';
+
+      } else if (buffer[i] == oe
+          || buffer[i] == oe_se) {
+
+        buffer[i] = 'o';
+
+      } else if (buffer[i] == OE
+          || buffer[i] == OE_se) {
+
+        buffer[i] = 'O';
+
+      } else if ((buffer[i] == 'a' || buffer[i] == 'A')
+          && (buffer[i + 1] == 'a'
+          || buffer[i + 1] == 'A'
+          || buffer[i + 1] == 'e'
+          || buffer[i + 1] == 'E'
+          || buffer[i + 1] == 'o'
+          || buffer[i + 1] == 'O')
+          ) {
+
+        length = StemmerUtil.delete(buffer, i + 1, length);
+
+      } else if ((buffer[i] == 'o' || buffer[i] == 'O')
+          && (buffer[i + 1] == 'e'
+          || buffer[i + 1] == 'E'
+          || buffer[i + 1] == 'o'
+          || buffer[i + 1] == 'O')
+          ) {
+
+        length = StemmerUtil.delete(buffer, i + 1, length);
+
+      }
+    }
+
+    charTermAttribute.setLength(length);
+
+
+    return true;
+  }
+
+}
+
Index: analysis/common/src/test/org/apache/lucene/analysis/miscellaneous/TestScandinavianFoldingFilter.java
===================================================================
--- analysis/common/src/test/org/apache/lucene/analysis/miscellaneous/TestScandinavianFoldingFilter.java	(revision 0)
+++ analysis/common/src/test/org/apache/lucene/analysis/miscellaneous/TestScandinavianFoldingFilter.java	(arbetskopia)
@@ -0,0 +1,72 @@
+package org.apache.lucene.analysis.miscellaneous;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (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.
+ */
+
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.core.KeywordTokenizer;
+import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
+
+import java.io.StringReader;
+import java.util.HashSet;
+import java.util.Set;
+
+import junit.framework.TestCase;
+
+public class TestScandinavianFoldingFilter extends TestCase {
+
+
+  public void test() throws Exception {
+
+
+    assertEquals("aaaeea", fold("aeäaeeeae"));
+    assertEquals("aaeea", fold("aeaeeeae"));
+
+    assertEquals("boen", fold("bøen"));
+    assertEquals("aene", fold("åene"));
+
+
+    assertEquals("blabarsyltetoj", fold("blåbærsyltetøj"));
+    assertEquals("raksmorgas", fold("räksmörgås"));
+    assertEquals("raksmorgas", fold("raeksmörgaos"));
+    assertEquals("raksmorgas", fold("raeksmoergås"));
+
+
+    String[][] equalTermsMatrix = new String[][]{
+        new String[]{"blåbærsyltetøj", "blaabaarsyltetoej", "blåbärsyltetöj"},
+        new String[]{"räksmörgås", "raksmorgas", "ræksmørgås", "raeksmoergaas", "ræksmörgaos"},
+    };
+
+    for (String[] equalTerms : equalTermsMatrix) {
+      Set<String> value = new HashSet<String>();
+      for (String equalTerm : equalTerms) {
+        value.add(fold(equalTerm));
+      }
+      assertTrue(value.size() == 1);
+    }
+
+
+
+  }
+
+  private String fold(String value) throws Exception {
+    TokenStream ts = new ScandinavianFoldingFilter(new KeywordTokenizer(new StringReader(value)));
+    ts.incrementToken();
+    CharTermAttribute attribute = ts.getAttribute(CharTermAttribute.class);
+    return new String(attribute.buffer(), 0, attribute.length());
+  }
+}