diff -r 5bf94ed61975 -r 77c47a56e1f7 bldsystemtools/sysdeftools/mergesysdef.xsl
--- a/bldsystemtools/sysdeftools/mergesysdef.xsl	Tue Jul 13 15:47:33 2010 +0100
+++ b/bldsystemtools/sysdeftools/mergesysdef.xsl	Thu Jul 22 16:44:43 2010 +0100
@@ -22,10 +22,16 @@
 <xsl:variable name="downstream" select="document($Downstream,.)/SystemDefinition"/>
 <xsl:param name="upname">
 	<xsl:choose>
-		<xsl:when test="$downstream[starts-with(@schema,'2.') or starts-with(@schema,'1.')  or not(systemModel)]">
+		<xsl:when test="$downstream[starts-with(@schema,'2.') or starts-with(@schema,'1.')]">
 			<xsl:message terminate="yes">Syntax <xsl:value-of select="@schema"/> not supported</xsl:message>
 		</xsl:when>
-		<xsl:when test="/SystemDefinition/systemModel/@name=$downstream/systemModel/@name">
+		<xsl:when test="name($downstream/*)!=name(/SystemDefinition/*)">
+			<xsl:message terminate="yes">Can only merge fragments of the same rank</xsl:message>
+		</xsl:when>
+<!--		<xsl:when test="$downstream[not(systemModel)]">
+			<xsl:message terminate="yes">Needs to be a standalone system definition</xsl:message>
+		</xsl:when>-->
+		<xsl:when test="/SystemDefinition/systemModel/@name=$downstream/systemModel/@name or not(/SystemDefinition/systemModel/@name)">
 			<xsl:apply-templates mode="origin-term" select="/*">
 				<xsl:with-param name="root">Upstream</xsl:with-param>
 			</xsl:apply-templates>
@@ -36,11 +42,14 @@
 
 <xsl:param name="downname">
 	<xsl:choose>
-		<xsl:when test="/SystemDefinition/systemModel/@name=$downstream/systemModel/@name">
+		<xsl:when test="/SystemDefinition/systemModel/@name=$downstream/systemModel/@name or not($downstream/systemModel/@name)">
 			<xsl:apply-templates mode="origin-term" select="$downstream">	
 				<xsl:with-param name="root">Downstream</xsl:with-param>
 			</xsl:apply-templates>
 			</xsl:when>
+		<xsl:when test="name($downstream/*)!=name(/SystemDefinition/*)">
+			<xsl:message terminate="yes">Can only merge fragments of the same rank</xsl:message>
+		</xsl:when>
 		<xsl:otherwise><xsl:value-of select="$downstream/systemModel/@name"/></xsl:otherwise>
 	</xsl:choose>
 </xsl:param>
@@ -68,7 +77,21 @@
 </xsl:template>
 
 
-<!--  this merge only two files according to the 3.0.0 rules. Old syntax not supported. Must be converetd before calling -->
+<!-- choose the greater of the two versions -->
+<xsl:template name="compare-versions"><xsl:param name="v1"/><xsl:param name="v2"/>
+			<xsl:choose>
+				<xsl:when test="$v1=$v2"><xsl:value-of select="$v1"/></xsl:when>
+				<xsl:when test="substring-before($v1,'.') &gt; substring-before($v2,'.')"><xsl:value-of select="$v1"/></xsl:when>
+				<xsl:when test="substring-before($v1,'.') &lt; substring-before($v2,'.')"><xsl:value-of select="$v2"/></xsl:when>
+				<xsl:when test="substring-before(substring-after($v1,'.'),'.') &gt; substring-before(substring-after($v2,'.'),'.')"><xsl:value-of select="$v1"/></xsl:when>
+				<xsl:when test="substring-before(substring-after($v1,'.'),'.') &lt; substring-before(substring-after($v2,'.'),'.')"><xsl:value-of select="$v2"/></xsl:when>
+				<xsl:when test="substring-after(substring-after($v1,'.'),'.') &gt; substring-after(substring-after($v2,'.'),'.')"><xsl:value-of select="$v1"/></xsl:when>
+				<xsl:when test="substring-after(substring-after($v1,'.'),'.') &lt; substring-after(substring-after($v2,'.'),'.')"><xsl:value-of select="$v2"/></xsl:when>
+				<xsl:otherwise><xsl:value-of select="$v1"/></xsl:otherwise>
+			</xsl:choose>
+</xsl:template>
+
+<!--  this merge only two files according to the 3.0.x rules. Old syntax not supported. Must be converetd before calling -->