[552823] Fix GraphML labels on operation edges
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLBuilder.java b/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLBuilder.java
index c7ad071..80da212 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLBuilder.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLBuilder.java
@@ -228,7 +228,7 @@
 		s.pushTag("y:PolyLineEdge");
 		appendLineStyle(new LineStyle(lineColor, LineType.valueOf(lineType)));
 		appendArrows(sourceArrowType, targetArrowType);
-		appendEdgeLabel(label, lineColor, null);
+		appendEdgeLabel(lineColor, label, null, null);
 		s.popTag();
 		s.popTag();
 		s.popTag();
@@ -263,7 +263,7 @@
 		s.popTag();
 	}
 
-	protected void appendEdgeLabel(@Nullable String sourceLabel, String labelColor, @Nullable String targetLabel) {
+	protected void appendEdgeLabel(String labelColor, @Nullable String sourceLabel, @Nullable String midLabel, @Nullable String targetLabel) {
 		if (sourceLabel !=  null) {
 			s.pushTag("y:EdgeLabel");
 			s.appendElement("textColor", labelColor);
@@ -271,6 +271,13 @@
 			s.appendElement("modelPosition", "thead");
 			s.appendValueAndPopTag(sourceLabel);
 		}
+		if (midLabel !=  null) {
+			s.pushTag("y:EdgeLabel");
+			s.appendElement("textColor", labelColor);
+			s.appendElement("modelName", "six_pos");
+			s.appendElement("modelPosition", "head");
+			s.appendValueAndPopTag(midLabel);
+		}
 		if (targetLabel !=  null) {
 			s.pushTag("y:EdgeLabel");
 			s.appendElement("textColor", labelColor);
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLStringBuilder.java b/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLStringBuilder.java
index 42406a3..267d3be 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLStringBuilder.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/graphs/GraphMLStringBuilder.java
@@ -78,7 +78,7 @@
 		s.pushTag("y:PolyLineEdge");
 		appendLineStyle(new LineStyle(lineColor, lineType, width));
 		appendArrows(sourceArrowType != null ? sourceArrowType.name() : ArrowType.none.name(), targetArrowType != null ? targetArrowType.name() : ArrowType.delta.name());
-		appendEdgeLabel(sourceLabel, labelColor, targetLabel);
+		appendEdgeLabel(labelColor, sourceLabel, label, targetLabel);
 		s.popTag();
 		s.popTag();
 		s.popTag();