diff --git a/topics/transformation/empty.xbgf b/topics/transformation/empty.xbgf
deleted file mode 100644
index 470e7b34..00000000
--- a/topics/transformation/empty.xbgf
+++ /dev/null
@@ -1,4 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<xbgf:sequence xmlns:xbgf="http://planet-sl.org/xbgf" xmlns:bgf="http://planet-sl.org/bgf">
-	<xbgf:dump/>
-</xbgf:sequence>
diff --git a/topics/transformation/normalization/empty.xbgf b/topics/transformation/normalization/empty.xbgf
new file mode 100644
index 00000000..4db90fdc
--- /dev/null
+++ b/topics/transformation/normalization/empty.xbgf
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xbgf:sequence xmlns:xbgf="http://planet-sl.org/xbgf" xmlns:bgf="http://planet-sl.org/bgf">
+	<!-- an ugly replacement for a noop/id/skip command that is lacking in xbgf now -->
+	<xbgf:introduce>
+		<bgf:production>
+			<nonterminal>temporary_nonterminal_name_which_is_unique</nonterminal>
+			<bgf:expression>
+				<epsilon/>
+			</bgf:expression>
+		</bgf:production>
+	</xbgf:introduce>
+	<xbgf:eliminate>
+		<nonterminal>temporary_nonterminal_name_which_is_unique</nonterminal>
+	</xbgf:eliminate>
+</xbgf:sequence>
diff --git a/topics/transformation/normalization/subdefs/extract.xslt b/topics/transformation/normalization/subdefs/extract.xslt
index d4f2162b..0596ad42 100644
--- a/topics/transformation/normalization/subdefs/extract.xslt
+++ b/topics/transformation/normalization/subdefs/extract.xslt
@@ -21,7 +21,7 @@
 				<bgf:production>
 					<nonterminal>
 						<xsl:value-of select="$name"/>
-						<xsl:text>-grp-</xsl:text>
+						<xsl:text>_grp_</xsl:text>
 						<xsl:value-of select="position()"/>
 					</nonterminal>
 					<bgf:expression>
diff --git a/topics/transformation/normalization/subdefs/inline.xslt b/topics/transformation/normalization/subdefs/inline.xslt
index 79c0241d..67a85275 100644
--- a/topics/transformation/normalization/subdefs/inline.xslt
+++ b/topics/transformation/normalization/subdefs/inline.xslt
@@ -4,7 +4,7 @@
 	<xsl:template match="/bgf:grammar">
 		<xbgf:sequence xmlns:bgf="http://planet-sl.org/bgf" xmlns:xbgf="http://planet-sl.org/xbgf">
 			<xsl:for-each select="bgf:production">
-				<xsl:if test="contains(nonterminal,'-grp-')">
+				<xsl:if test="contains(nonterminal,'_grp_')">
 					<xbgf:inline>
 						<xsl:value-of select="nonterminal"/>
 					</xbgf:inline>