diff --git a/shared/prolog/readXbgf.pro b/shared/prolog/readXbgf.pro
index ad1378ac..4762bc1f 100644
--- a/shared/prolog/readXbgf.pro
+++ b/shared/prolog/readXbgf.pro
@@ -347,10 +347,11 @@ xml2xbgf(T,unchain(P2))
     child(name(bgf:production),T,P1),
     xmlToP(P1,P2).
 
-xml2xbgf(T,undefine(N))
+xml2xbgf(T,undefine(Ns2))
  :-
     self(name(xbgf:undefine),T),
-    content(T,N).
+    children(name(nonterminal),T,Ns1),
+    maplist(content,Ns1,Ns2).
 
 xml2xbgf(T,redefine(Ps2))
  :-
diff --git a/shared/prolog/xbgf1.pro b/shared/prolog/xbgf1.pro
index 776b5dc0..b7fd9851 100644
--- a/shared/prolog/xbgf1.pro
+++ b/shared/prolog/xbgf1.pro
@@ -109,7 +109,7 @@ ps2n(Ps1,N)
 redefine(Ps1,G1,G2)
  :-
     ps2n(Ps1,N),
-    undefine(N,G1,G3),
+    undefine1(N,G1,G3),
     define(Ps1,G3,G2).
 
 
@@ -1379,8 +1379,13 @@ unchain(P1,g(Rs,Ps1),g(Rs,Ps4))
 %
 % Undefine a nonterminal, i.e., remove all productions
 %
+undefine([],g(Rs1,Ps1),g(Rs1,Ps1)).
+undefine([N|Ns],g(Rs1,Ps1),g(Rs3,Ps3))
+ :-
+    undefine1(N,g(Rs1,Ps1),g(Rs2,Ps2)),
+    undefine(Ns,g(Rs2,Ps2),g(Rs3,Ps3)).
 
-undefine(N,g(Rs1,Ps1),g(Rs2,Ps2))
+undefine1(N,g(Rs1,Ps1),g(Rs2,Ps2))
  :-
     definedNs(Ps1,Defined),
     require(
diff --git a/shared/xsd/slps-xsd.csproj b/shared/xsd/slps-xsd.csproj
index 67d8f74e..702d1c44 100644
--- a/shared/xsd/slps-xsd.csproj
+++ b/shared/xsd/slps-xsd.csproj
@@ -10,7 +10,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>slps_xsd</RootNamespace>
     <AssemblyName>slps-xsd</AssemblyName>
-    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <FileUpgradeFlags>
     </FileUpgradeFlags>
@@ -32,6 +32,7 @@
     <IsWebBootstrapper>false</IsWebBootstrapper>
     <UseApplicationTrust>false</UseApplicationTrust>
     <BootstrapperEnabled>true</BootstrapperEnabled>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -59,6 +60,7 @@
   </Target>
   -->
   <ItemGroup>
+    <None Include="app.config" />
     <None Include="bgf.xsd" />
     <None Include="btf.xsd" />
     <None Include="edd.xsd">
diff --git a/shared/xsd/xbgf.xsd b/shared/xsd/xbgf.xsd
index 0c30d1fe..cd2205b1 100644
--- a/shared/xsd/xbgf.xsd
+++ b/shared/xsd/xbgf.xsd
@@ -1084,11 +1084,10 @@
       </xsd:documentation>
     </xsd:annotation>
     <xsd:complexType>
-      <xsd:simpleContent>
-        <xsd:extension base="bgf:nonterminal">
-          <xsd:attribute name="tag" type="xsd:string"/>
-        </xsd:extension>
-      </xsd:simpleContent>
+      <xsd:sequence>
+        <xsd:element name="nonterminal" type="bgf:nonterminal" maxOccurs="unbounded"/>
+      </xsd:sequence>
+      <xsd:attribute name="tag" type="xsd:string"/>
     </xsd:complexType>
   </xsd:element>
 
diff --git a/shared/xsl/slps-xsl.csproj b/shared/xsl/slps-xsl.csproj
index b2bcb916..3560dcc3 100644
--- a/shared/xsl/slps-xsl.csproj
+++ b/shared/xsl/slps-xsl.csproj
@@ -10,7 +10,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>slps_xsl</RootNamespace>
     <AssemblyName>slps-xsl</AssemblyName>
-    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <FileUpgradeFlags>
     </FileUpgradeFlags>
@@ -32,6 +32,7 @@
     <IsWebBootstrapper>false</IsWebBootstrapper>
     <UseApplicationTrust>false</UseApplicationTrust>
     <BootstrapperEnabled>true</BootstrapperEnabled>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -97,4 +98,7 @@
       <Install>true</Install>
     </BootstrapperPackage>
   </ItemGroup>
+  <ItemGroup>
+    <None Include="app.config" />
+  </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/shared/xsl/xbgf2xbnf.xslt b/shared/xsl/xbgf2xbnf.xslt
index a391af6c..117ba9c8 100644
--- a/shared/xsl/xbgf2xbnf.xslt
+++ b/shared/xsl/xbgf2xbnf.xslt
@@ -5,7 +5,7 @@
     xmlns:xhtml="http://www.w3.org/1999/xhtml">
 
   <xsl:import href="bgf2bnf.xslt" />
-  
+
   <xsl:output
       method="text"
       encoding="UTF-8"
@@ -39,7 +39,7 @@
       </xsl:when>
     </xsl:choose>
   </xsl:template>
-  
+
   <!-- chain, define, ... -->
 
   <xsl:template match="xbgf:*">
@@ -91,7 +91,19 @@
 </xsl:text>
   </xsl:template>
 
-  <xsl:template match="xbgf:deyaccify|xbgf:eliminate|xbgf:horizontal|xbgf:inline|xbgf:undefine">
+  <xsl:template match="xbgf:undefine">
+    <xsl:value-of select="local-name()" />
+    <xsl:text>(</xsl:text>
+    <xsl:value-of select="*[1]/text()"/>
+    <xsl:for-each select="*[position()>1]">
+      <xsl:text>, </xsl:text>
+      <xsl:value-of select="text()"/>
+    </xsl:for-each>
+    <xsl:text>);
+</xsl:text>
+  </xsl:template>
+
+  <xsl:template match="xbgf:deyaccify|xbgf:eliminate|xbgf:horizontal|xbgf:inline">
     <xsl:value-of select="local-name()" />
     <xsl:text>(</xsl:text>
     <xsl:value-of select="text()"/>
@@ -198,7 +210,7 @@
     <xsl:text>);
 </xsl:text>
   </xsl:template>
-  
+
   <xsl:template match="xbgf:reroot">
     <xsl:value-of select="local-name()" />
     <xsl:text>(</xsl:text>
@@ -258,4 +270,4 @@
 </xsl:text>
   </xsl:template>
 
-</xsl:stylesheet>
+</xsl:stylesheet>
\ No newline at end of file
diff --git a/topics/java/lci/java-lci.csproj b/topics/java/lci/java-lci.csproj
index f507eb48..e8581478 100644
--- a/topics/java/lci/java-lci.csproj
+++ b/topics/java/lci/java-lci.csproj
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
@@ -10,8 +10,29 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>java_lci</RootNamespace>
     <AssemblyName>java-lci</AssemblyName>
-    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
+    <FileUpgradeFlags>
+    </FileUpgradeFlags>
+    <UpgradeBackupLocation>
+    </UpgradeBackupLocation>
+    <OldToolsVersion>3.5</OldToolsVersion>
+    <PublishUrl>publish\</PublishUrl>
+    <Install>true</Install>
+    <InstallFrom>Disk</InstallFrom>
+    <UpdateEnabled>false</UpdateEnabled>
+    <UpdateMode>Foreground</UpdateMode>
+    <UpdateInterval>7</UpdateInterval>
+    <UpdateIntervalUnits>Days</UpdateIntervalUnits>
+    <UpdatePeriodically>false</UpdatePeriodically>
+    <UpdateRequired>false</UpdateRequired>
+    <MapFileExtensions>true</MapFileExtensions>
+    <ApplicationRevision>0</ApplicationRevision>
+    <ApplicationVersion>1.0.0.%2a</ApplicationVersion>
+    <IsWebBootstrapper>false</IsWebBootstrapper>
+    <UseApplicationTrust>false</UseApplicationTrust>
+    <BootstrapperEnabled>true</BootstrapperEnabled>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -54,6 +75,7 @@
     <None Include="..\..\..\shared\xsd\xbgf.xsd">
       <Link>xbgf.xsd</Link>
     </None>
+    <None Include="app.config" />
     <None Include="java.lcf" />
     <None Include="xbgf\correct-impl1.xbgf" />
     <None Include="xbgf\correct-impl2.xbgf" />
@@ -126,4 +148,26 @@
     <None Include="xbgf\rename-read21.xbgf" />
     <None Include="xbgf\rename-read3.xbgf" />
   </ItemGroup>
+  <ItemGroup>
+    <BootstrapperPackage Include="Microsoft.Net.Client.3.5">
+      <Visible>False</Visible>
+      <ProductName>.NET Framework 3.5 SP1 Client Profile</ProductName>
+      <Install>false</Install>
+    </BootstrapperPackage>
+    <BootstrapperPackage Include="Microsoft.Net.Framework.3.5.SP1">
+      <Visible>False</Visible>
+      <ProductName>.NET Framework 3.5 SP1</ProductName>
+      <Install>true</Install>
+    </BootstrapperPackage>
+    <BootstrapperPackage Include="Microsoft.VisualBasic.PowerPacks.10.0">
+      <Visible>False</Visible>
+      <ProductName>Microsoft Visual Basic PowerPacks 10.0</ProductName>
+      <Install>true</Install>
+    </BootstrapperPackage>
+    <BootstrapperPackage Include="Microsoft.Windows.Installer.3.1">
+      <Visible>False</Visible>
+      <ProductName>Windows Installer 3.1</ProductName>
+      <Install>true</Install>
+    </BootstrapperPackage>
+  </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/topics/java/lci/java-lci.sln b/topics/java/lci/java-lci.sln
index 4480a20f..3b4c288d 100644
--- a/topics/java/lci/java-lci.sln
+++ b/topics/java/lci/java-lci.sln
@@ -1,6 +1,5 @@
-
-Microsoft Visual Studio Solution File, Format Version 10.00
-# Visual C# Express 2008
+Microsoft Visual Studio Solution File, Format Version 11.00
+# Visual Studio 2010
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "java-lci", "java-lci.csproj", "{9DF685A6-6572-47F9-8DE3-1E827BFDB62F}"
 EndProject
 Global
diff --git a/topics/java/lci/xbgf/correct-impl2.xbgf b/topics/java/lci/xbgf/correct-impl2.xbgf
index 8eda2e23..53dafd05 100644
--- a/topics/java/lci/xbgf/correct-impl2.xbgf
+++ b/topics/java/lci/xbgf/correct-impl2.xbgf
@@ -214,7 +214,9 @@
   <!--   undefine lexical term -->
   <!-- GENERALITY -->
   <!-- RELAXATION -->
-  <xbgf:undefine>Identifier</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>Identifier</nonterminal>
+  </xbgf:undefine>
 
   <!-- ISSUE CORRECT SPECERROR
   Real error in JLS2:
diff --git a/topics/java/lci/xbgf/correct-impl3.xbgf b/topics/java/lci/xbgf/correct-impl3.xbgf
index 59f63826..2a06d3bd 100644
--- a/topics/java/lci/xbgf/correct-impl3.xbgf
+++ b/topics/java/lci/xbgf/correct-impl3.xbgf
@@ -187,7 +187,9 @@ Annotation:
   <!--   undefine lexical term -->
   <!-- GENERALITY -->
   <!-- RELAXATION -->
-  <xbgf:undefine>Identifier</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>Identifier</nonterminal>
+  </xbgf:undefine>
 
   <!-- ISSUE CORRECT SPECERROR -->
   <!-- not right because VariableDeclarator starts with Identifier:
diff --git a/topics/java/lci/xbgf/edit-read2.xbgf b/topics/java/lci/xbgf/edit-read2.xbgf
index 6e5acd4c..bd24e281 100644
--- a/topics/java/lci/xbgf/edit-read2.xbgf
+++ b/topics/java/lci/xbgf/edit-read2.xbgf
@@ -8,7 +8,9 @@
      { [ ExplicitConstructorInvocation ] [ BlockStatements ] }
   -->
   <!-- RELAXATION -->
-  <xbgf:undefine>ConstructorBody</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>ConstructorBody</nonterminal>
+  </xbgf:undefine>
   <!-- RELAXATION -->
   <xbgf:unite>
     <add>ConstructorBody</add>
diff --git a/topics/java/lci/xbgf/inlineStatements.xbgf b/topics/java/lci/xbgf/inlineStatements.xbgf
index b8239e3a..3850a6b3 100644
--- a/topics/java/lci/xbgf/inlineStatements.xbgf
+++ b/topics/java/lci/xbgf/inlineStatements.xbgf
@@ -136,7 +136,9 @@
   <xbgf:inline>IfThenStatement</xbgf:inline>
   <!-- GENERALITY -->
   <!-- RELAXATION -->
-  <xbgf:undefine>StatementNoShortIf</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>StatementNoShortIf</nonterminal>
+  </xbgf:undefine>
   <xbgf:eliminate>WhileStatementNoShortIf</xbgf:eliminate>
   <xbgf:eliminate>IfThenElseStatementNoShortIf</xbgf:eliminate>
   <xbgf:eliminate>ForStatementNoShortIf</xbgf:eliminate>
diff --git a/topics/java/lci/xbgf/refactorExpressions.xbgf b/topics/java/lci/xbgf/refactorExpressions.xbgf
index 3e596338..05da9861 100644
--- a/topics/java/lci/xbgf/refactorExpressions.xbgf
+++ b/topics/java/lci/xbgf/refactorExpressions.xbgf
@@ -725,21 +725,16 @@ vs
     </xbgf:vertical>
   </xbgf:atomic>
   <!-- BREFACTOR -->
-  <xbgf:undefine>MultiplicativeExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>AdditiveExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>ShiftExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>RelationalExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>EqualityExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>AndExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>ExclusiveOrExpression</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>InclusiveOrExpression</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>MultiplicativeExpression</nonterminal>
+    <nonterminal>AdditiveExpression</nonterminal>
+    <nonterminal>ShiftExpression</nonterminal>
+    <nonterminal>RelationalExpression</nonterminal>
+    <nonterminal>EqualityExpression</nonterminal>
+    <nonterminal>AndExpression</nonterminal>
+    <nonterminal>ExclusiveOrExpression</nonterminal>
+    <nonterminal>InclusiveOrExpression</nonterminal>
+  </xbgf:undefine>
   <xbgf:eliminate>ConditionalAndExpression</xbgf:eliminate>
 
   <!-- And now "Expression1" -->
@@ -823,9 +818,10 @@ vs
 
   <!-- last effort for Expression1-->
   <!-- BREFACTOR -->
-  <xbgf:undefine>LeftHandSide</xbgf:undefine>
-  <!-- BREFACTOR -->
-  <xbgf:undefine>Assignment</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>LeftHandSide</nonterminal>
+    <nonterminal>Assignment</nonterminal>
+  </xbgf:undefine>
   <!-- RELAXATION -->
   <xbgf:remove>
     <vertical>
diff --git a/topics/java/lci/xbgf/refactorInterfaces-read3.xbgf b/topics/java/lci/xbgf/refactorInterfaces-read3.xbgf
index ae6d9e2d..3ba8b913 100644
--- a/topics/java/lci/xbgf/refactorInterfaces-read3.xbgf
+++ b/topics/java/lci/xbgf/refactorInterfaces-read3.xbgf
@@ -646,7 +646,9 @@
   ExceptionTypeList vs QualifiedIdentifierList -->
   <!-- GENERALITY -->
   <!-- RELAXATION -->
-  <xbgf:undefine>ExceptionTypeList</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>ExceptionTypeList</nonterminal>
+  </xbgf:undefine>
   <!-- RELAXATION -->
   <xbgf:unite>
     <add>ExceptionTypeList</add>
diff --git a/topics/java/lci/xbgf/refactorStatements-jls1.xbgf b/topics/java/lci/xbgf/refactorStatements-jls1.xbgf
index ef9f640a..a6d38e14 100644
--- a/topics/java/lci/xbgf/refactorStatements-jls1.xbgf
+++ b/topics/java/lci/xbgf/refactorStatements-jls1.xbgf
@@ -274,7 +274,9 @@
 
   <!-- Getting rid of all of them -->
   <!-- BREFACTOR -->
-  <xbgf:undefine>StatementNoShortIf</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>StatementNoShortIf</nonterminal>
+  </xbgf:undefine>
   <xbgf:eliminate>ForStatementNoShortIf</xbgf:eliminate>
   <xbgf:eliminate>WhileStatementNoShortIf</xbgf:eliminate>
   <xbgf:eliminate>LabeledStatementNoShortIf</xbgf:eliminate>
diff --git a/topics/languedoc/xbgf/xldf/completeRevSections.xldf b/topics/languedoc/xbgf/xldf/completeRevSections.xldf
index a2dcc6ea..bc05c446 100644
--- a/topics/languedoc/xbgf/xldf/completeRevSections.xldf
+++ b/topics/languedoc/xbgf/xldf/completeRevSections.xldf
@@ -37,6 +37,68 @@
       </bgf:production>
     </xbgf:project>
   </xldf:transformGrammar>
+  <xldf:transformGrammar>
+    <target>undefine</target>
+    <xbgf:anonymize>
+      <bgf:production>
+        <nonterminal>undefine</nonterminal>
+        <bgf:expression>
+          <sequence>
+            <bgf:expression>
+              <plus>
+              <bgf:expression> <marked>
+                <bgf:expression>
+                  <selectable>
+                    <selector>nonterminal</selector>
+                    <bgf:expression>
+                      <nonterminal>nonterminal</nonterminal>
+                    </bgf:expression>
+                  </selectable>
+                </bgf:expression>
+              </marked> </bgf:expression>
+              </plus>
+            </bgf:expression>
+            <bgf:expression>
+                  <selectable>
+                    <selector>tag</selector>
+                    <bgf:expression>
+                      <value>string</value>
+                    </bgf:expression>
+                  </selectable>
+                </bgf:expression>
+          </sequence>
+        </bgf:expression>
+      </bgf:production>
+    </xbgf:anonymize>
+    <xbgf:project>
+      <bgf:production>
+        <nonterminal>undefine</nonterminal>
+        <bgf:expression>
+          <sequence>
+            <bgf:expression>
+              <plus>
+                <bgf:expression>
+                  <nonterminal>nonterminal</nonterminal>
+                </bgf:expression>
+              </plus>
+            </bgf:expression>
+            <bgf:expression>
+              <marked>
+                <bgf:expression>
+                  <selectable>
+                    <selector>tag</selector>
+                    <bgf:expression>
+                      <value>string</value>
+                    </bgf:expression>
+                  </selectable>
+                </bgf:expression>
+              </marked>
+            </bgf:expression>
+          </sequence>
+        </bgf:expression>
+      </bgf:production>
+    </xbgf:project>
+  </xldf:transformGrammar>
   <xldf:transformGrammar>
     <target>inject</target>
     <xbgf:project>
diff --git a/topics/transformation/xbgf/tests/undefine.baseline b/topics/transformation/xbgf/tests/undefine1.baseline
similarity index 100%
rename from topics/transformation/xbgf/tests/undefine.baseline
rename to topics/transformation/xbgf/tests/undefine1.baseline
diff --git a/topics/transformation/xbgf/tests/undefine.bgf b/topics/transformation/xbgf/tests/undefine1.bgf
similarity index 100%
rename from topics/transformation/xbgf/tests/undefine.bgf
rename to topics/transformation/xbgf/tests/undefine1.bgf
diff --git a/topics/transformation/xbgf/tests/undefine.xbgf b/topics/transformation/xbgf/tests/undefine1.xbgf
similarity index 61%
rename from topics/transformation/xbgf/tests/undefine.xbgf
rename to topics/transformation/xbgf/tests/undefine1.xbgf
index bb760744..d4ccedca 100644
--- a/topics/transformation/xbgf/tests/undefine.xbgf
+++ b/topics/transformation/xbgf/tests/undefine1.xbgf
@@ -1,5 +1,7 @@
 <xbgf:sequence
   xmlns:bgf="http://planet-sl.org/bgf"
   xmlns:xbgf="http://planet-sl.org/xbgf">
-  <xbgf:undefine>op</xbgf:undefine>
+  <xbgf:undefine>
+    <nonterminal>op</nonterminal>
+  </xbgf:undefine>
 </xbgf:sequence>
diff --git a/topics/transformation/xbgf/tests/undefine2.baseline b/topics/transformation/xbgf/tests/undefine2.baseline
new file mode 100644
index 00000000..c2fa8955
--- /dev/null
+++ b/topics/transformation/xbgf/tests/undefine2.baseline
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<bgf:grammar xmlns:bgf="http://planet-sl.org/bgf">
+  <bgf:production>
+    <nonterminal>foo</nonterminal>
+    <bgf:expression>
+      <nonterminal>bar</nonterminal>
+    </bgf:expression>
+  </bgf:production>
+  <bgf:production>
+    <nonterminal>wez</nonterminal>
+    <bgf:expression>
+      <nonterminal>qux</nonterminal>
+    </bgf:expression>
+  </bgf:production>
+</bgf:grammar>
\ No newline at end of file
diff --git a/topics/transformation/xbgf/tests/undefine2.bgf b/topics/transformation/xbgf/tests/undefine2.bgf
new file mode 100644
index 00000000..3f25216e
--- /dev/null
+++ b/topics/transformation/xbgf/tests/undefine2.bgf
@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<bgf:grammar xmlns:bgf="http://planet-sl.org/bgf">
+  <bgf:production>
+    <nonterminal>foo</nonterminal>
+    <bgf:expression>
+      <nonterminal>bar</nonterminal>
+    </bgf:expression>
+  </bgf:production>
+  <bgf:production>
+    <nonterminal>bar</nonterminal>
+    <bgf:expression>
+      <nonterminal>wez</nonterminal>
+    </bgf:expression>
+  </bgf:production>
+  <bgf:production>
+    <nonterminal>wez</nonterminal>
+    <bgf:expression>
+      <nonterminal>qux</nonterminal>
+    </bgf:expression>
+  </bgf:production>
+  <bgf:production>
+    <nonterminal>qux</nonterminal>
+    <bgf:expression>
+      <nonterminal>foo</nonterminal>
+    </bgf:expression>
+  </bgf:production>
+</bgf:grammar>
\ No newline at end of file
diff --git a/topics/transformation/xbgf/tests/undefine2.xbgf b/topics/transformation/xbgf/tests/undefine2.xbgf
new file mode 100644
index 00000000..38e50532
--- /dev/null
+++ b/topics/transformation/xbgf/tests/undefine2.xbgf
@@ -0,0 +1,8 @@
+<xbgf:sequence
+  xmlns:bgf="http://planet-sl.org/bgf"
+  xmlns:xbgf="http://planet-sl.org/xbgf">
+  <xbgf:undefine>
+    <nonterminal>bar</nonterminal>
+    <nonterminal>qux</nonterminal>
+  </xbgf:undefine>
+</xbgf:sequence>