Index: src/test/org/apache/lucene/search/CheckHits.java
===================================================================
--- src/test/org/apache/lucene/search/CheckHits.java	(revision 543620)
+++ src/test/org/apache/lucene/search/CheckHits.java	(working copy)
@@ -334,11 +334,77 @@
       
       TestCase.assertNotNull("Explanation of [["+d+"]] for #"+doc+" is null",
                              exp);
-      TestCase.assertEquals("Score of [["+d+"]] for #"+doc+
-                            " does not match explanation: " + exp.toString(),
-                            score, exp.getValue(), SCORE_TOLERANCE_DELTA);
+      verifyExplanation(q,doc,score,exp);
     }
     
+    // check that an explanation has the expected score, and that its
+    // sub-details max/sum/factor match to that score.
+    private static void verifyExplanation (Query q, int doc, float score, Explanation expl) {
+      float value = expl.getValue();
+      TestCase.assertEquals(q+": score(doc="+doc+")="+score+
+          " != explanationScore="+value+" Explanation: "+expl,
+          score,value,SCORE_TOLERANCE_DELTA);
+      Explanation detail[] = expl.getDetails();
+      if (detail!=null) {
+        if (detail.length==1) {
+          // simple containment, no matter what the description says, just verify contained expl has same score
+          verifyExplanation(q,doc,score,detail[0]);
+        } else {
+          // explanation must either:
+          // - end with one of: "product of:", "sum of:", "max of:", or
+          // - have "max plus <x> times others" (where <x> is float).
+          float x = 0;
+          String descr = expl.getDescription().toLowerCase();
+          boolean productOf = descr.endsWith("product of:");
+          boolean sumOf = descr.endsWith("sum of:");
+          boolean maxOf = descr.endsWith("max of:");
+          boolean maxTimesOthers = false;
+          if (!(productOf || sumOf || maxOf)) {
+            // maybe 'max plus x times others'
+            int k1 = descr.indexOf("max plus ");
+            if (k1>=0) {
+              k1 += "max plus ".length();
+              int k2 = descr.indexOf(" ",k1);
+              try {
+                x = Float.parseFloat(descr.substring(k1,k2).trim());
+                if (descr.substring(k2).trim().equals("times others of:")) {
+                  maxTimesOthers = true;
+                }
+              } catch (NumberFormatException e) {
+              }
+            }
+          }
+          TestCase.assertTrue(
+              q+": multi valued explanation description="+descr+" must be 'max of plus x times others' or end with 'prodoct of' or 'sum of:' or 'max of:' - "+expl,
+              productOf || sumOf || maxOf || maxTimesOthers);
+          float sum = 0;
+          float product = 1;
+          float max = 0;
+          for (int i=0; i<detail.length; i++) {
+            float dval = detail[i].getValue();
+            verifyExplanation(q,doc,dval,detail[i]);
+            product *= dval;
+            sum += dval;
+            max = Math.max(max,dval);
+          }
+          float combined = 0;
+          if (productOf) {
+            combined = product;
+          } else if (sumOf) {
+            combined = sum;
+          } else if (maxOf) {
+            combined = max;
+          } else if (maxTimesOthers) {
+            combined = max + x * (sum - max);
+          } else {
+              TestCase.assertTrue("should never get here!",false);
+          }
+          TestCase.assertEquals(q+": actual subDetails combined=="+combined+
+              " != value="+value+" Explanation: "+expl,
+              combined,value,SCORE_TOLERANCE_DELTA);
+        }
+      }
+    }
   }
 
 }
Index: src/test/org/apache/lucene/search/TestSimpleExplanations.java
===================================================================
--- src/test/org/apache/lucene/search/TestSimpleExplanations.java	(revision 543620)
+++ src/test/org/apache/lucene/search/TestSimpleExplanations.java	(working copy)
@@ -17,26 +17,6 @@
  * limitations under the License.
  */
 
-
-import org.apache.lucene.store.RAMDirectory;
-
-import org.apache.lucene.index.IndexWriter;
-import org.apache.lucene.index.IndexReader;
-import org.apache.lucene.index.Term;
-
-import org.apache.lucene.analysis.WhitespaceAnalyzer;
-
-import org.apache.lucene.document.Document;
-import org.apache.lucene.document.Field;
-
-import org.apache.lucene.queryParser.QueryParser;
-import org.apache.lucene.queryParser.ParseException;
-
-import junit.framework.TestCase;
-
-import java.util.Random;
-import java.util.BitSet;
-
 /**
  * TestExplanations subclass focusing on basic query types
  */
Index: src/test/org/apache/lucene/search/QueryUtils.java
===================================================================
--- src/test/org/apache/lucene/search/QueryUtils.java	(revision 543620)
+++ src/test/org/apache/lucene/search/QueryUtils.java	(working copy)
@@ -64,15 +64,22 @@
     // happens, please change test to use a different example.
     TestCase.assertTrue(q1.hashCode() != q2.hashCode());
   }
-
-
+  
+  /** check that explanations of a query 'score' correctly */
+  public static void checkExplanations (final Query q, final Searcher s) throws IOException {
+    s.search(q,new CheckHits.ExplanationAsserter(q,null,s));
+  }
+  
   /** various query sanity checks on a searcher */
   public static void check(Query q1, Searcher s) {
     try {
       check(q1);
-      if (s!=null && s instanceof IndexSearcher) {
-        IndexSearcher is = (IndexSearcher)s;
-        checkSkipTo(q1,is);
+      if (s!=null) {
+        if (s instanceof IndexSearcher) {
+          IndexSearcher is = (IndexSearcher)s;
+          checkSkipTo(q1,is);
+        }
+        checkExplanations(q1,s);
       }
     } catch (IOException e) {
       throw new RuntimeException(e);
Index: src/java/org/apache/lucene/search/payloads/BoostingTermQuery.java
===================================================================
--- src/java/org/apache/lucene/search/payloads/BoostingTermQuery.java	(revision 543620)
+++ src/java/org/apache/lucene/search/payloads/BoostingTermQuery.java	(working copy)
@@ -166,7 +166,7 @@
         //GSI: I suppose we could toString the payload, but I don't think that would be a good idea 
         payloadBoost.setDescription("scorePayload(...)");
         result.setValue(nonPayloadExpl.getValue() * avgPayloadScore);
-        result.setDescription("btq");
+        result.setDescription("btq, product of:");
         return result;
       }
     }
Index: src/java/org/apache/lucene/search/FilteredQuery.java
===================================================================
--- src/java/org/apache/lucene/search/FilteredQuery.java	(revision 543620)
+++ src/java/org/apache/lucene/search/FilteredQuery.java	(working copy)
@@ -79,7 +79,12 @@
       }
       public Explanation explain (IndexReader ir, int i) throws IOException {
         Explanation inner = weight.explain (ir, i);
-        inner.setValue(getBoost() * inner.getValue());
+        if (getBoost()!=1) {
+          Explanation preBoost = inner;
+          inner = new Explanation(inner.getValue()*getBoost(),"product of:");
+          inner.addDetail(new Explanation(getBoost(),"boost"));
+          inner.addDetail(preBoost);
+        }
         Filter f = FilteredQuery.this.filter;
         BitSet matches = f.bits(ir);
         if (matches.get(i))