Index: CHANGES.txt
===================================================================
--- CHANGES.txt	(revision 803466)
+++ CHANGES.txt	(working copy)
@@ -88,7 +88,9 @@
     compat break and caused custom SpanQuery implementations to fail at runtime
     in a variety of ways. This issue attempts to remedy things by causing
     a compile time break on custom SpanQuery implementations and removing 
-    the PayloadSpans class, with its functionality now moved to Spans.
+    the PayloadSpans class, with its functionality now moved to Spans. To
+    help in alleviating future back compat pain, Spans has been changed from
+    an interface to an abstract class.
     (Hugh Cayless, Mark Miller)
  
 Changes in runtime behavior
@@ -374,7 +376,9 @@
     compat break and caused custom SpanQuery implementations to fail at runtime
     in a variety of ways. This issue attempts to remedy things by causing
     a compile time break on custom SpanQuery implementations and removing 
-    the PayloadSpans class, with its functionality now moved to Spans.
+    the PayloadSpans class, with its functionality now moved to Spans. To
+    help in alleviating future back compat pain, Spans has been changed from
+    an interface to an abstract class.
     (Hugh Cayless, Mark Miller)
 
 Bug fixes
Index: src/java/org/apache/lucene/search/spans/NearSpansOrdered.java
===================================================================
--- src/java/org/apache/lucene/search/spans/NearSpansOrdered.java	(revision 803466)
+++ src/java/org/apache/lucene/search/spans/NearSpansOrdered.java	(working copy)
@@ -51,7 +51,7 @@
  * Expert:
  * Only public for subclassing.  Most implementations should not need this class
  */
-public class NearSpansOrdered implements Spans {
+public class NearSpansOrdered extends Spans {
   private final int allowedSlop;
   private boolean firstTime = true;
   private boolean more = false;
Index: src/java/org/apache/lucene/search/spans/NearSpansUnordered.java
===================================================================
--- src/java/org/apache/lucene/search/spans/NearSpansUnordered.java	(revision 803466)
+++ src/java/org/apache/lucene/search/spans/NearSpansUnordered.java	(working copy)
@@ -31,7 +31,7 @@
  * Expert:
  * Only public for subclassing.  Most implementations should not need this class
  */
-public class NearSpansUnordered implements Spans {
+public class NearSpansUnordered extends Spans {
   private SpanNearQuery query;
 
   private List ordered = new ArrayList();         // spans in query order
@@ -67,7 +67,7 @@
 
 
   /** Wraps a Spans, and can be used to form a linked list. */
-  private class SpansCell implements Spans {
+  private class SpansCell extends Spans {
     private Spans spans;
     private SpansCell next;
     private int length = -1;
Index: src/java/org/apache/lucene/search/spans/Spans.java
===================================================================
--- src/java/org/apache/lucene/search/spans/Spans.java	(revision 803466)
+++ src/java/org/apache/lucene/search/spans/Spans.java	(working copy)
@@ -24,9 +24,9 @@
  * Each span represents a range of term positions within a document.  Matches
  * are enumerated in order, by increasing document number, within that by
  * increasing start position and finally by increasing end position. */
-public interface Spans {
+public abstract class Spans {
   /** Move to the next match, returning true iff any such exists. */
-  boolean next() throws IOException;
+  public abstract boolean next() throws IOException;
 
   /** Skips to the first match beyond the current, whose document number is
    * greater than or equal to <i>target</i>. <p>Returns true iff there is such
@@ -41,16 +41,16 @@
    * </pre>
    * Most implementations are considerably more efficient than that.
    */
-  boolean skipTo(int target) throws IOException;
+  public abstract boolean skipTo(int target) throws IOException;
 
   /** Returns the document number of the current match.  Initially invalid. */
-  int doc();
+  public abstract int doc();
 
   /** Returns the start position of the current match.  Initially invalid. */
-  int start();
+  public abstract int start();
 
   /** Returns the end position of the current match.  Initially invalid. */
-  int end();
+  public abstract int end();
   
   /**
    * Returns the payload data for the current span.
@@ -75,22 +75,16 @@
    * @throws java.io.IOException
     */
   // TODO: Remove warning after API has been finalized
-  Collection/*<byte[]>*/ getPayload() throws IOException;
+  public abstract Collection/*<byte[]>*/ getPayload() throws IOException;
 
   /**
    * Checks if a payload can be loaded at this position.
    * <p/>
    * Payloads can only be loaded once per call to
    * {@link #next()}.
-   * <p/>
-   * <p><font color="#FF0000">
-   * WARNING: The status of the <b>Payloads</b> feature is experimental.
-   * The APIs introduced here might change in the future and will not be
-   * supported anymore in such a case.</font>
    *
    * @return true if there is a payload available at this position that can be loaded
    */
-  // TODO: Remove warning after API has been finalized
-  public boolean isPayloadAvailable();
+  public abstract boolean isPayloadAvailable();
 
 }
Index: src/java/org/apache/lucene/search/spans/TermSpans.java
===================================================================
--- src/java/org/apache/lucene/search/spans/TermSpans.java	(revision 803466)
+++ src/java/org/apache/lucene/search/spans/TermSpans.java	(working copy)
@@ -27,7 +27,7 @@
  * Expert:
  * Public for extension only
  */
-public class TermSpans implements Spans {
+public class TermSpans extends Spans {
   protected TermPositions positions;
   protected Term term;
   protected int doc;
Index: src/test/org/apache/lucene/search/spans/JustCompileSearchSpans.java
===================================================================
--- src/test/org/apache/lucene/search/spans/JustCompileSearchSpans.java	(revision 803466)
+++ src/test/org/apache/lucene/search/spans/JustCompileSearchSpans.java	(working copy)
@@ -35,7 +35,7 @@
 
   private static final String UNSUPPORTED_MSG = "unsupported: used for back-compat testing only !";
 
-  static final class JustCompileSpans implements Spans {
+  static final class JustCompileSpans extends Spans {
 
     public int doc() {
       throw new UnsupportedOperationException(UNSUPPORTED_MSG);
@@ -88,7 +88,7 @@
     
   }
 
-  static final class JustCompilePayloadSpans implements Spans {
+  static final class JustCompilePayloadSpans extends Spans {
 
     public Collection getPayload() throws IOException {
       throw new UnsupportedOperationException(UNSUPPORTED_MSG);