From b73fa6a4e95a50aa70d8b25809132f7eccb59f24 Mon Sep 17 00:00:00 2001
From: Wendell Piez <wendell.piez@nist.gov>
Date: Wed, 8 Jul 2020 17:47:18 -0400
Subject: [PATCH] #39, #53, usnistgov/OSCAL#633. JSON->supermodel conversion.
 Metapath mapping corrections. Nearly working round-trip test conversion.

---
 .../xslt-M4/compose/unfold-model-map.xsl      |   2 +-
 .../converter-gen/produce-json-converter.xsl  |  17 +-
 .../converter-gen/produce-xml-converter.xsl   |  74 +++---
 .../xslt-M4/metapath/metapath-jsonize.xsl     |  34 ++-
 .../metapath/metapath-jsonizing-result.html   | 247 +++++++++++++++---
 .../xslt-M4/metapath/metapath-jsonizing.xspec |  79 +++++-
 .../xslt-M4/metapath/parse-metapath.xsl       |  15 +-
 .../xslt-M4/testing/models_metaschema.xml     |   6 +-
 .../testing/test-xml-json-roundtrip.xpl       | 202 ++++++++++++++
 .../xslt-M4/validate/metaschema-check.sch     |   1 +
 10 files changed, 579 insertions(+), 98 deletions(-)
 create mode 100644 toolchains/xslt-M4/testing/test-xml-json-roundtrip.xpl

diff --git a/toolchains/xslt-M4/compose/unfold-model-map.xsl b/toolchains/xslt-M4/compose/unfold-model-map.xsl
index 8828f1456..84df5fd0b 100644
--- a/toolchains/xslt-M4/compose/unfold-model-map.xsl
+++ b/toolchains/xslt-M4/compose/unfold-model-map.xsl
@@ -17,7 +17,7 @@
     <xsl:template match="*[exists(@group-name)]">
         <group name="{@group-name}" in-xml="{ if (@group-xml='GROUPED') then 'SHOWN' else 'HIDDEN' }"
             max-occurs="1" min-occurs="{ if (@min-occurs='0') then '0' else '1'}">
-            <xsl:copy-of select="@json-key-flag | @group-json"/>
+            <xsl:copy-of select="@json-key-flag | @group-json | @recursive"/>
             <xsl:next-match/>
         </group>
     </xsl:template>
diff --git a/toolchains/xslt-M4/converter-gen/produce-json-converter.xsl b/toolchains/xslt-M4/converter-gen/produce-json-converter.xsl
index 329a0abd3..299804929 100644
--- a/toolchains/xslt-M4/converter-gen/produce-json-converter.xsl
+++ b/toolchains/xslt-M4/converter-gen/produce-json-converter.xsl
@@ -56,7 +56,12 @@
         <xsl:variable name="matching-xml">
             <xsl:apply-templates select="." mode="make-xml-match"/>
         </xsl:variable>
-        <xsl:text expand-text="true">(: { $matching-xml} :) { m:jsonize-path($matching-xml) }</xsl:text>
+        <!--<xsl:try select="m:jsonize-path($matching-xml)">
+            <xsl:catch>
+                <xsl:message expand-text="true" xmlns:err="http://www.w3.org/2005/xqt-errors">(On { @name }) { $matching-xml }: { $err:description }</xsl:message>
+            </xsl:catch>
+        </xsl:try>-->
+        <xsl:text expand-text="true"><!--(: { $matching-xml} :) -->{ m:jsonize-path($matching-xml) }</xsl:text>
         <!--<xsl:sequence select="m:jsonize-path($matching-xml)"/>-->
         
     </xsl:template>
@@ -71,7 +76,7 @@
     
     <!-- Overriding interface template -->
     <xsl:template match="*" mode="make-pull">
-        <pull who="{name()}[@key='{@key}']"/>
+        <XSLT:apply-templates select="*[@key='{@key}']"/>
         <!--<pull>
             <xsl:copy>
                 <xsl:copy-of select="@*"/>
@@ -80,6 +85,12 @@
         <!--<xsl:apply-templates select="." mode="make-xml-pull"/>-->
     </xsl:template>
     
-    
+    <xsl:template name="comment-template">
+        <xsl:comment expand-text="true">
+            <xsl:text> Cf XML match="</xsl:text>
+            <xsl:apply-templates select="." mode="make-xml-match"/>
+            <xsl:text>" </xsl:text>
+        </xsl:comment>
+    </xsl:template>
     
 </xsl:stylesheet>
\ No newline at end of file
diff --git a/toolchains/xslt-M4/converter-gen/produce-xml-converter.xsl b/toolchains/xslt-M4/converter-gen/produce-xml-converter.xsl
index 24df75e35..8a43dbd35 100644
--- a/toolchains/xslt-M4/converter-gen/produce-xml-converter.xsl
+++ b/toolchains/xslt-M4/converter-gen/produce-xml-converter.xsl
@@ -57,24 +57,25 @@
             <!-- first we produce templates for (each) of the global definitions.-->
             <xsl:for-each-group select="//*[@scope = 'global'][not(@recursive='true')]"
                 group-by="string-join((local-name(), @name), ':')">
-                <!-- These are all the same so we do only one -->
-                <xsl:apply-templates select="current-group()[1]" mode="make-template">
-                    <xsl:with-param name="ilk" select="current-group()"/>
+                <!-- These are all the same so we do only one, but we pass in the group to construct the match -->
+                <xsl:apply-templates select="current-group()[1]" mode="make-template-for-global">
+                    <xsl:with-param name="team" tunnel="true" select="current-group()"/>
                 </xsl:apply-templates>
             </xsl:for-each-group>
 
-            <!-- next we produce templates for local definitions -->
+            <!-- next we produce templates for local definitions - a receiving template
+                 filters out the globals ... -->
             <xsl:apply-templates select=".//assembly | .//field | .//flag" mode="make-template-for-local"/>
 
             <!--finally, if needed, a template for copying prose across, stripping ns -->
-            <xsl:call-template name="cast-prose-template"/>
+            <xsl:call-template name="for-this-converter"/>
             
         </XSLT:stylesheet> 
     </xsl:template>
     
     
     <xsl:template name="xpath-namespace">
-        <xsl:attribute name="xpath-default-namespace" expand-text="true">{ $source-namespace }</xsl:attribute>
+        <xsl:attribute name="xpath-default-namespace" select="$source-namespace"/>
     </xsl:template>
     
     <xsl:template name="make-strip-space">
@@ -84,8 +85,20 @@
     <xsl:template name="initial-comment">
         <xsl:comment> METASCHEMA conversion stylesheet supports XML -> METASCHEMA/SUPERMODEL conversion </xsl:comment>
     </xsl:template>
+
+    <xsl:template name="provide-namespace">
+        <!-- iff at the top -->
+        <xsl:for-each select="parent::model" expand-text="true">
+            <!-- likewise the XSLT provides a namespace only if at the top -->
+            <XSLT:if test=". is /*">
+                <XSLT:attribute name="namespace">{ $source-namespace }</XSLT:attribute>
+                <!-- don't need unless we have a requirement to prefix in serialization: <XSLT:attribute name="prefix">{ $source-prefix }</XSLT:attribute>-->
+            </XSLT:if>
+        </xsl:for-each>
+    </xsl:template>
     
-    <xsl:template name="cast-prose-template">
+    <xsl:template name="for-this-converter">
+        <!-- For the XML converter, we need a generic template to cast prose contents into the supermodel namespace -->
         <xsl:if test="exists(//value[@as-type = ('markup-line', 'markup-multiline')])">
             <XSLT:template match="*" mode="cast-prose">
                 <XSLT:element name="{{ local-name() }}"
@@ -97,18 +110,16 @@
         </xsl:if>
     </xsl:template>
     
-
-
     <xsl:template match="*[@scope='global']" mode="make-template-for-local"/>
     
     <xsl:template match="*" mode="make-template-for-local">
-        <xsl:apply-templates select="." mode="make-template"/>
+        <xsl:apply-templates select="." mode="make-template-for-global"/>
     </xsl:template>
  
     <!-- no template for implicit wrappers on markup-multiline -->
-    <xsl:template priority="2" match="field[empty(@gi)][value/@as-type='markup-multiline']" mode="make-template"/>
+    <xsl:template priority="2" match="field[empty(@gi)][value/@as-type='markup-multiline']" mode="make-template-for-global"/>
         
-    <xsl:template match="*" mode="make-template">
+    <xsl:template match="*" mode="make-template-for-global">
         <xsl:variable name="matching">
             <xsl:apply-templates select="." mode="make-match"/>
         </xsl:variable>
@@ -117,6 +128,7 @@
             <!-- A parameter allows the call to drop the key, necessary for recursive
                 groups of elements also allowed at the root (at least) -->
             <XSLT:param name="with-key" select="true()"/>
+            <xsl:call-template name="comment-template"/>
             <xsl:element name="{ local-name() }" namespace="http://csrc.nist.gov/ns/oscal/metaschema/1.0/supermodel">
                 <xsl:copy-of select="@* except (@key|@scope)"/>
                 <!--'SCALAR' marks fields that will be strings or data values, not maps (objects)
@@ -136,39 +148,34 @@
             </xsl:element>
         </XSLT:template>
         <!--Additionally we need templates for elements defined implicitly as wrappers for given assemblies or fields-->
-        <xsl:apply-templates select="parent::group[exists(@gi)]" mode="make-template"/>
+        <xsl:apply-templates select="parent::group[exists(@gi)]" mode="make-template-for-global"/>
     </xsl:template>
     
-    <xsl:template name="provide-namespace">
-        <!-- iff at the top -->
-        <xsl:for-each select="parent::model" expand-text="true">
-            <!-- likewise the XSLT provides a namespace only if at the top -->
-            <XSLT:if test=". is /*">
-                <XSLT:attribute name="namespace">{ $source-namespace }</XSLT:attribute>
-                <!-- don't need unless we have a requirement to prefix in serialization: <XSLT:attribute name="prefix">{ $source-prefix }</XSLT:attribute>-->
-            </XSLT:if>
-        </xsl:for-each>
-    </xsl:template>
-    
-    <xsl:template match="flag" mode="make-template">
+    <xsl:template match="flag" mode="make-template-for-global">
         <xsl:variable name="matching">
             <xsl:apply-templates select="." mode="make-match"/>
         </xsl:variable>
         <XSLT:template match="{ $matching}">
+            <xsl:call-template name="comment-template"/>
             <flag>
                 <xsl:copy-of select="@* except @scope"/>
-                <XSLT:value-of select="."/>     
+                <XSLT:value-of select="."/>
             </flag>
         </XSLT:template>
     </xsl:template>
     
     <xsl:template priority="11" match="flag" mode="make-xml-match">
-        <xsl:value-of>
-            <xsl:apply-templates select=".." mode="make-xml-match"/>
-            <xsl:text>/</xsl:text>
-            <xsl:value-of select="'@' || @gi"/>
-        </xsl:value-of>
-        
+        <xsl:param name="team" tunnel="true" select="."/>
+        <xsl:variable name="team-matches" as="xs:string*">
+            <xsl:for-each select="$team">
+                <xsl:value-of>
+                    <xsl:apply-templates select=".." mode="make-xml-match"/>
+                    <xsl:text>/@</xsl:text>
+                    <xsl:value-of select="@gi"/>
+                </xsl:value-of>
+            </xsl:for-each>
+        </xsl:variable>
+        <xsl:value-of select="distinct-values($team-matches)" separator=" | "/>
     </xsl:template>
     
     <xsl:template priority="11" match="flag" mode="make-xml-step">
@@ -284,5 +291,8 @@
         <XSLT:value-of select="."/>
     </xsl:template>
     
+    <!-- stub for override   -->
+    <xsl:template name="comment-template"/>
+        
     
 </xsl:stylesheet>
\ No newline at end of file
diff --git a/toolchains/xslt-M4/metapath/metapath-jsonize.xsl b/toolchains/xslt-M4/metapath/metapath-jsonize.xsl
index 522dd5036..d1cdb6802 100644
--- a/toolchains/xslt-M4/metapath/metapath-jsonize.xsl
+++ b/toolchains/xslt-M4/metapath/metapath-jsonize.xsl
@@ -9,6 +9,7 @@
     exclude-result-prefixes="#all"
     expand-text="true">
     
+    <xsl:output indent="yes"/>
     <!-- xmlns:p="xpath20" -->
     <!--<xsl:import href="REx/xpath20.xslt"/>-->
     
@@ -60,13 +61,15 @@
         <!--<test>field-flagged-groupable</test>
         <test>field-dynamic-value-key</test>-->
         <!--<test>*/@color</test>-->
-        <test>field-by-key/@id</test>
-        <test>field-dynamic-value-key/@id</test>
+        <test>wrapped-assemblies</test>
+        <test>EVERYTHING/@id|field-named-value/@id</test>
+        
+        <!--<test>field-dynamic-value-key/@id</test>
         
         <test>field-1only/(value() + path)</test>
         
         <test>/EVERYTHING/(field-1only | field-named-value)</test>
-        <test>/*</test>
+        <test>/*</test>-->
         <!--<test>field-named-value/value()</test>-->
         
         <!--field with dynamic value key?-->
@@ -97,12 +100,12 @@
     
     <xsl:template match="test" mode="testing">
         <xsl:variable name="map" select="m:path-map(string(.))"/>
-        <test expr="{.}" expand="{string($map)}" json-path="{m:jsonize-path(.)}">
+        <test expr="{.}" expand="{string-join($map)}" json-path="{m:jsonize-path(.)}">
         <!--<test>-->
             <!--<xsl:apply-templates select="key('obj-by-gi',.,$definition-map)" mode="cast-node-test"/>-->
-            <!--<xsl:sequence select="m:jsonize-path(.)"/>
-            <xsl:sequence select="m:path-map(.)"/>-->
-            <!--<xsl:sequence select="p:parse-XPath(.)"/>-->
+            <!--<xsl:sequence select="m:jsonize-path(.)"/>-->
+            <xsl:sequence select="m:path-map(.)"/>
+            <xsl:sequence select="p:parse-XPath(.)"/>
         </test>
     </xsl:template>
     
@@ -118,9 +121,14 @@
         <cast>{$px}:array[@key='{../@key}']/{$px}:map</cast>
     </xsl:template>
     
+    <!-- Catches groups that are explicit in the XML -->
+    <xsl:template match="group[exists(@gi)]" mode="cast-node-test">
+        <cast>{$px}:array[@key='{@key}']</cast>
+    </xsl:template>
+    
     <!-- Catches assembly grouped as SINGLETON_OR_ARRAY -->
     <xsl:template match="group/assembly" mode="cast-node-test">
-        <cast>{$px}:assembly[@key='{../@key}']/{$px}:map</cast>
+        <cast>{$px}:array[@key='{../@key}']/{$px}:map</cast>
         <cast>{$px}:map[@key='{../@key}']</cast>
     </xsl:template>
     
@@ -220,11 +228,11 @@
         <xsl:variable name="not-value-filter">
             <xsl:text expand-text="true">[not(@key=({ string-join($not-value-flags ! ( '''' || . || ''''), ',' ) }))]</xsl:text>
         </xsl:variable>
-        <cast>{$px}:{$value-type}{ $not-value-filter[matches(.,'\S')]}</cast>
+        <cast>{$px}:{$value-type}{ $not-value-filter[matches(.,'\S')]}/@key</cast>
     </xsl:template>
     
     <xsl:template match="*" mode="cast-node-test" expand-text="true">
-        <!--<cast>OoopsFellThroughOn{ name() }</cast>-->
+        <cast>OoopsFellThroughOn { name() }</cast>
         <cast>{$px}:*[@key='{../@key}']</cast>
     </xsl:template>
     
@@ -267,7 +275,7 @@
     
     <xsl:template match="@as-type[. = $numeric-types]" mode="json-type">number</xsl:template>
        
-    <xsl:function name="m:path-map" as="node()">
+    <xsl:function name="m:path-map" as="node()*">
         <xsl:param name="expr"/>
         <xsl:variable name="parse.tree" select="p:parse-XPath($expr)"/>
         <xsl:apply-templates select="$parse.tree" mode="path-map"/>
@@ -288,11 +296,11 @@
     </xsl:function>
     
     <!-- m:jsonization returns the path mapped step by step into JSON, as an XML element tree -->
-    <xsl:function name="m:jsonization" as="element()">
+    <xsl:function name="m:jsonization" as="node()*">
         <xsl:param name="metapath" as="xs:string" required="yes"/>
         <xsl:variable name="path-map" select="m:path-map($metapath)"/>
         <xsl:choose>
-            <xsl:when test="$path-map instance of element()">
+            <xsl:when test="exists($path-map/*)">
                 <xsl:apply-templates select="$path-map" mode="cast-path"/>
             </xsl:when>
             <xsl:otherwise>
diff --git a/toolchains/xslt-M4/metapath/metapath-jsonizing-result.html b/toolchains/xslt-M4/metapath/metapath-jsonizing-result.html
index 4e61188be..a25cf070b 100644
--- a/toolchains/xslt-M4/metapath/metapath-jsonizing-result.html
+++ b/toolchains/xslt-M4/metapath/metapath-jsonizing-result.html
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?><html xmlns="http://www.w3.org/1999/xhtml">
    <head>
       <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
-      <title>Test Report for C:/Users/wap1/Documents/usnistgov/metaschema/toolchains/xslt-M4/metapath/metapath-jsonize.xsl (passed: 12 / pending: 0 / failed: 0 / total: 12)</title>
+      <title>Test Report for C:/Users/wap1/Documents/usnistgov/metaschema/toolchains/xslt-M4/metapath/metapath-jsonize.xsl (passed: 14 / pending: 0 / failed: 2 / total: 16)</title>
       <style type="text/css">/****************************************************************************/
 /*  File:       test-report.css                                             */
 /*  Author:     Jeni Tennison                                               */
@@ -511,7 +511,7 @@
       <h1>Test Report</h1>
       <p>Stylesheet: <a href="file:/C:/Users/wap1/Documents/usnistgov/metaschema/toolchains/xslt-M4/metapath/metapath-jsonize.xsl">C:/Users/wap1/Documents/usnistgov/metaschema/toolchains/xslt-M4/metapath/metapath-jsonize.xsl</a></p>
       <p>XSpec: <a href="file:/C:/Users/wap1/Documents/usnistgov/metaschema/toolchains/xslt-M4/metapath/metapath-jsonizing.xspec">C:/Users/wap1/Documents/usnistgov/metaschema/toolchains/xslt-M4/metapath/metapath-jsonizing.xspec</a></p>
-      <p>Tested: 7 July 2020 at 14:47</p>
+      <p>Tested: 8 July 2020 at 16:23</p>
       <h2>Contents</h2>
       <table class="xspec">
          <colgroup>
@@ -524,10 +524,10 @@ <h2>Contents</h2>
          <thead>
             <tr>
                <th></th>
-               <th class="totals">passed: 12</th>
+               <th class="totals">passed: 14</th>
                <th class="totals">pending: 0</th>
-               <th class="totals">failed: 0</th>
-               <th class="totals">total: 12</th>
+               <th class="totals">failed: 2</th>
+               <th class="totals">total: 16</th>
             </tr>
          </thead>
          <tbody>
@@ -538,78 +538,106 @@ <h2>Contents</h2>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
+            <tr class="failed">
+               <th><a href="#top_scenario2">Problem case</a></th>
+               <th class="totals">0</th>
+               <th class="totals">0</th>
+               <th class="totals">1</th>
+               <th class="totals">1</th>
+            </tr>
+            <tr class="failed">
+               <th><a href="#top_scenario3">Problem case</a></th>
+               <th class="totals">0</th>
+               <th class="totals">0</th>
+               <th class="totals">1</th>
+               <th class="totals">1</th>
+            </tr>
             <tr class="successful">
-               <th><a href="#top_scenario2">Path to root (path map)</a></th>
+               <th><a href="#top_scenario4">Path to root (path map)</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario3">Path to root (mapped structure)</a></th>
+               <th><a href="#top_scenario5">Path to root (mapped structure)</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario4">Not a path</a></th>
+               <th><a href="#top_scenario6">Not a path</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario5">Nominal document element</a></th>
+               <th><a href="#top_scenario7">Nominal document element</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario6">A field with flags</a></th>
+               <th><a href="#top_scenario8">A field with flags</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario7">Absolute path to specified document element</a></th>
+               <th><a href="#top_scenario9">Absolute path to specified document element</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario8">A path to a node not described in the definition map</a></th>
+               <th><a href="#top_scenario10">A path to a node not described in the definition map</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario9">Absolute path to document element, with predicate</a></th>
+               <th><a href="#top_scenario11">Absolute path to document element, with predicate</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario10">Absolute path to document element, with predicate including a relative path</a></th>
+               <th><a href="#top_scenario12">Absolute path to document element, with predicate including a relative path</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario11">Absolute path showing two steps into a recursive structure</a></th>
+               <th><a href="#top_scenario13">Relative path to flag (path map)</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
                <th class="totals">1</th>
             </tr>
             <tr class="successful">
-               <th><a href="#top_scenario12">Relative path showing three steps into a recursive structure</a></th>
+               <th><a href="#top_scenario14">Compound path to flags (path map)</a></th>
+               <th class="totals">1</th>
+               <th class="totals">0</th>
+               <th class="totals">0</th>
+               <th class="totals">1</th>
+            </tr>
+            <tr class="successful">
+               <th><a href="#top_scenario15">Absolute path showing two steps into a recursive structure</a></th>
+               <th class="totals">1</th>
+               <th class="totals">0</th>
+               <th class="totals">0</th>
+               <th class="totals">1</th>
+            </tr>
+            <tr class="successful">
+               <th><a href="#top_scenario16">Relative path showing three steps into a recursive structure</a></th>
                <th class="totals">1</th>
                <th class="totals">0</th>
                <th class="totals">0</th>
@@ -637,8 +665,113 @@ <h2 class="successful">Path to root<span class="scenario-totals">passed: 1 / pen
          </table>
       </div>
       <div id="top_scenario2">
-         <h2 class="successful">Path to root (path map)<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
+         <h2 class="failed">Problem case<span class="scenario-totals">passed: 0 / pending: 0 / failed: 1 / total: 1</span></h2>
          <table class="xspec" id="table_scenario2">
+            <colgroup>
+               <col style="width:75%" />
+               <col style="width:25%" />
+            </colgroup>
+            <tbody>
+               <tr class="failed">
+                  <th>Problem case</th>
+                  <th>passed: 0 / pending: 0 / failed: 1 / total: 1</th>
+               </tr>
+               <tr class="failed">
+                  <td><a href="#scenario2-expect1">structure XPath to root</a></td>
+                  <td>Failure</td>
+               </tr>
+            </tbody>
+         </table>
+         <div id="scenario2">
+            <h3>Problem case</h3>
+            <div id="scenario2-expect1" class="xTestReport">
+               <h4 class="xTestReportTitle">structure XPath to root</h4>
+               <div class="xTestReportHint"><a href="https://github.com/xspec/xspec/wiki/Understanding-Test-Results" target="_blank" title="What does this report mean?">❔</a></div>
+               <table class="xspecResult">
+                  <thead>
+                     <tr>
+                        <th>Result</th>
+                        <th>Expected Result</th>
+                     </tr>
+                  </thead>
+                  <tbody>
+                     <tr>
+                        <td>
+                           <pre>'(j:array[@key=''EVERYTHING''] | j:array[@key=''''])'</pre>
+                        </td>
+                        <td>
+                           <pre>'j:array[@key=''wrapped-assemblies'']/j:map | j:map[@key=''wrapped-assemblies'']'</pre>
+                        </td>
+                     </tr>
+                  </tbody>
+               </table>
+            </div>
+         </div>
+      </div>
+      <div id="top_scenario3">
+         <h2 class="failed">Problem case<span class="scenario-totals">passed: 0 / pending: 0 / failed: 1 / total: 1</span></h2>
+         <table class="xspec" id="table_scenario3">
+            <colgroup>
+               <col style="width:75%" />
+               <col style="width:25%" />
+            </colgroup>
+            <tbody>
+               <tr class="failed">
+                  <th>Problem case</th>
+                  <th>passed: 0 / pending: 0 / failed: 1 / total: 1</th>
+               </tr>
+               <tr class="failed">
+                  <td><a href="#scenario3-expect1">structure XPath to root</a></td>
+                  <td>Failure</td>
+               </tr>
+            </tbody>
+         </table>
+         <div id="scenario3">
+            <h3>Problem case</h3>
+            <div id="scenario3-expect1" class="xTestReport">
+               <h4 class="xTestReportTitle">structure XPath to root</h4>
+               <div class="xTestReportHint"><a href="https://github.com/xspec/xspec/wiki/Understanding-Test-Results" target="_blank" title="What does this report mean?">❔</a></div>
+               <table class="xspecResult">
+                  <thead>
+                     <tr>
+                        <th>Result</th>
+                        <th>Expected Result</th>
+                     </tr>
+                  </thead>
+                  <tbody>
+                     <tr>
+                        <td>
+                           <p>XPath <code class="diff">/element()</code> from:</p>
+                           <pre>&lt;<span class="diff">m:metapath</span> xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0"&gt;
+   &lt;<span class="diff">m:alternative</span>&gt;
+      &lt;<span class="diff">m:path</span>&gt;
+         &lt;<span class="diff">split</span> xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0"&gt;<span class="diff">(</span>&lt;<span class="diff">step</span>&gt;
+               &lt;<span class="diff">axis</span> /&gt;
+               &lt;<span class="diff">node</span>&gt;
+                  &lt;<span class="diff">cast</span>&gt;<span class="diff">j:array[@key='EVERYTHING']</span>&lt;/cast&gt;
+               &lt;/node&gt;
+            &lt;/step&gt;<span class="diff"> | </span>&lt;<span class="diff">step</span>&gt;
+               &lt;<span class="diff">axis</span> /&gt;
+               &lt;<span class="diff">node</span>&gt;
+                  &lt;<span class="diff">cast</span>&gt;<span class="diff">j:array[@key='']</span>&lt;/cast&gt;
+               &lt;/node&gt;
+            &lt;/step&gt;<span class="diff">)</span>&lt;/split&gt;
+      &lt;/m:path&gt;
+   &lt;/m:alternative&gt;
+&lt;/m:metapath&gt;</pre>
+                        </td>
+                        <td>
+                           <pre>'j:array[@key=''wrapped-assemblies'']/j:map | j:map[@key=''wrapped-assemblies'']'</pre>
+                        </td>
+                     </tr>
+                  </tbody>
+               </table>
+            </div>
+         </div>
+      </div>
+      <div id="top_scenario4">
+         <h2 class="successful">Path to root (path map)<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
+         <table class="xspec" id="table_scenario4">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -655,9 +788,9 @@ <h2 class="successful">Path to root (path map)<span class="scenario-totals">pass
             </tbody>
          </table>
       </div>
-      <div id="top_scenario3">
+      <div id="top_scenario5">
          <h2 class="successful">Path to root (mapped structure)<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario3">
+         <table class="xspec" id="table_scenario5">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -674,9 +807,9 @@ <h2 class="successful">Path to root (mapped structure)<span class="scenario-tota
             </tbody>
          </table>
       </div>
-      <div id="top_scenario4">
+      <div id="top_scenario6">
          <h2 class="successful">Not a path<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario4">
+         <table class="xspec" id="table_scenario6">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -693,9 +826,9 @@ <h2 class="successful">Not a path<span class="scenario-totals">passed: 1 / pendi
             </tbody>
          </table>
       </div>
-      <div id="top_scenario5">
+      <div id="top_scenario7">
          <h2 class="successful">Nominal document element<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario5">
+         <table class="xspec" id="table_scenario7">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -712,9 +845,9 @@ <h2 class="successful">Nominal document element<span class="scenario-totals">pas
             </tbody>
          </table>
       </div>
-      <div id="top_scenario6">
+      <div id="top_scenario8">
          <h2 class="successful">A field with flags<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario6">
+         <table class="xspec" id="table_scenario8">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -731,9 +864,9 @@ <h2 class="successful">A field with flags<span class="scenario-totals">passed: 1
             </tbody>
          </table>
       </div>
-      <div id="top_scenario7">
+      <div id="top_scenario9">
          <h2 class="successful">Absolute path to specified document element<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario7">
+         <table class="xspec" id="table_scenario9">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -744,15 +877,15 @@ <h2 class="successful">Absolute path to specified document element<span class="s
                   <th>passed: 1 / pending: 0 / failed: 0 / total: 1</th>
                </tr>
                <tr class="successful">
-                  <td>definition map indicates two possible roots</td>
+                  <td>only one path for a root</td>
                   <td>Success</td>
                </tr>
             </tbody>
          </table>
       </div>
-      <div id="top_scenario8">
+      <div id="top_scenario10">
          <h2 class="successful">A path to a node not described in the definition map<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario8">
+         <table class="xspec" id="table_scenario10">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -769,9 +902,9 @@ <h2 class="successful">A path to a node not described in the definition map<span
             </tbody>
          </table>
       </div>
-      <div id="top_scenario9">
+      <div id="top_scenario11">
          <h2 class="successful">Absolute path to document element, with predicate<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario9">
+         <table class="xspec" id="table_scenario11">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -788,9 +921,9 @@ <h2 class="successful">Absolute path to document element, with predicate<span cl
             </tbody>
          </table>
       </div>
-      <div id="top_scenario10">
+      <div id="top_scenario12">
          <h2 class="successful">Absolute path to document element, with predicate including a relative path<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario10">
+         <table class="xspec" id="table_scenario12">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -807,9 +940,47 @@ <h2 class="successful">Absolute path to document element, with predicate includi
             </tbody>
          </table>
       </div>
-      <div id="top_scenario11">
+      <div id="top_scenario13">
+         <h2 class="successful">Relative path to flag (path map)<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
+         <table class="xspec" id="table_scenario13">
+            <colgroup>
+               <col style="width:75%" />
+               <col style="width:25%" />
+            </colgroup>
+            <tbody>
+               <tr class="successful">
+                  <th>Relative path to flag (path map)</th>
+                  <th>passed: 1 / pending: 0 / failed: 0 / total: 1</th>
+               </tr>
+               <tr class="successful">
+                  <td>structure XPath to root</td>
+                  <td>Success</td>
+               </tr>
+            </tbody>
+         </table>
+      </div>
+      <div id="top_scenario14">
+         <h2 class="successful">Compound path to flags (path map)<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
+         <table class="xspec" id="table_scenario14">
+            <colgroup>
+               <col style="width:75%" />
+               <col style="width:25%" />
+            </colgroup>
+            <tbody>
+               <tr class="successful">
+                  <th>Compound path to flags (path map)</th>
+                  <th>passed: 1 / pending: 0 / failed: 0 / total: 1</th>
+               </tr>
+               <tr class="successful">
+                  <td>structure XPath to root</td>
+                  <td>Success</td>
+               </tr>
+            </tbody>
+         </table>
+      </div>
+      <div id="top_scenario15">
          <h2 class="successful">Absolute path showing two steps into a recursive structure<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario11">
+         <table class="xspec" id="table_scenario15">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
@@ -826,9 +997,9 @@ <h2 class="successful">Absolute path showing two steps into a recursive structur
             </tbody>
          </table>
       </div>
-      <div id="top_scenario12">
+      <div id="top_scenario16">
          <h2 class="successful">Relative path showing three steps into a recursive structure<span class="scenario-totals">passed: 1 / pending: 0 / failed: 0 / total: 1</span></h2>
-         <table class="xspec" id="table_scenario12">
+         <table class="xspec" id="table_scenario16">
             <colgroup>
                <col style="width:75%" />
                <col style="width:25%" />
diff --git a/toolchains/xslt-M4/metapath/metapath-jsonizing.xspec b/toolchains/xslt-M4/metapath/metapath-jsonizing.xspec
index 9be3e2895..14d3d8dd2 100644
--- a/toolchains/xslt-M4/metapath/metapath-jsonizing.xspec
+++ b/toolchains/xslt-M4/metapath/metapath-jsonizing.xspec
@@ -2,6 +2,7 @@
 <x:description xmlns:x="http://www.jenitennison.com/xslt/xspec"
     xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0" stylesheet="metapath-jsonize.xsl">
     <x:param name="definition-map" href="../testing/models_definition-map.xml"/>
+    
     <x:scenario label="Path to root">
         <x:call function="m:jsonize-path">
             <x:param>/</x:param>
@@ -9,14 +10,29 @@
         <x:expect label="path to root" select="'/j:map'"/>
     </x:scenario>
     
+    <x:scenario label="Problem case">
+        <x:call function="m:jsonize-path">
+            <x:param>wrapped-assemblies</x:param>
+        </x:call>
+        <x:expect label="structure XPath to root" select="'j:array[@key=''wrapped-assemblies'']/j:map | j:map[@key=''wrapped-assemblies'']'"/>
+    </x:scenario>
+    
+    <x:scenario label="Problem case">
+        <x:call function="m:jsonization">
+            <x:param>wrapped-assemblies</x:param>
+        </x:call>
+        <x:expect label="structure XPath to root" select="'j:array[@key=''wrapped-assemblies'']/j:map | j:map[@key=''wrapped-assemblies'']'"/>
+    </x:scenario>
+    
     <x:scenario label="Path to root (path map)">
         <x:call function="m:path-map">
             <x:param>/</x:param>
         </x:call>
         <x:expect label="structure XPath to root">
-            <m:alternative xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
-                <m:path>/</m:path>
-            </m:alternative>
+            <m:metapath xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
+                <m:alternative>
+                    <m:path>/</m:path>
+                </m:alternative></m:metapath>
         </x:expect>
     </x:scenario>
     
@@ -25,9 +41,9 @@
             <x:param>/</x:param>
         </x:call>
         <x:expect label="structured JSONized XPath to root">
-            <m:alternative xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
+            <m:metapath xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0"><m:alternative>
                 <m:path>/j:map</m:path>
-            </m:alternative>
+            </m:alternative></m:metapath>
         </x:expect>
     </x:scenario>
     
@@ -61,7 +77,7 @@
         <x:call function="m:jsonize-path">
             <x:param>/EVERYTHING</x:param>
         </x:call>
-        <x:expect label="definition map indicates two possible roots"
+        <x:expect label="only one path for a root"
             select="'/j:map/j:map[@key=''EVERYTHING'']'"/>
     </x:scenario>
     
@@ -89,6 +105,57 @@
             select="'/j:map/j:map[@key=''EVERYTHING''][j:map[@key=''field-1only'']/j:string[@key=''STRVALUE'']=''x'']'"/>
     </x:scenario>
     
+    <x:scenario label="Relative path to flag (path map)">
+        <x:call function="m:path-map">
+            <x:param>EVERYTHING/@id</x:param>
+        </x:call>
+        <x:expect label="structure XPath to root">
+            <m:metapath xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
+                <m:alternative>
+                    <m:path>
+                        <m:step>
+                            <m:axis>child::</m:axis>
+                            <m:node>EVERYTHING</m:node>
+                        </m:step>/<m:step>
+                            <m:axis>attribute::</m:axis>
+                            <m:node>id</m:node>
+                        </m:step>
+                    </m:path>
+                </m:alternative>
+            </m:metapath>
+        </x:expect>
+    </x:scenario>
+    
+    <x:scenario label="Compound path to flags (path map)">
+        <x:call function="m:path-map">
+            <x:param>EVERYTHING/@id|field-named-value/@id</x:param>
+        </x:call>
+        <x:expect label="structure XPath to root">
+            <m:metapath xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0">
+                <m:alternative>
+                    <m:path>
+                        <m:step>
+                            <m:axis>child::</m:axis>
+                            <m:node>EVERYTHING</m:node>
+                        </m:step>/<m:step>
+                            <m:axis>attribute::</m:axis>
+                            <m:node>id</m:node>
+                        </m:step>
+                    </m:path>
+                </m:alternative>|<m:alternative>
+                    <m:path>
+                        <m:step>
+                            <m:axis>child::</m:axis>
+                            <m:node>field-named-value</m:node>
+                        </m:step>/<m:step>
+                            <m:axis>attribute::</m:axis>
+                            <m:node>id</m:node>
+                        </m:step>
+                    </m:path>
+                </m:alternative>
+            </m:metapath>
+        </x:expect>
+    </x:scenario>
     <!--<x:scenario label="Absolute path to document element, with predicate including a relative path (mapped structure)">
         <x:call function="m:jsonization">
             <x:param>/EVERYTHING[field-1only/value()='x']</x:param>
diff --git a/toolchains/xslt-M4/metapath/parse-metapath.xsl b/toolchains/xslt-M4/metapath/parse-metapath.xsl
index 6a3b2e6ea..4ad06a2b4 100644
--- a/toolchains/xslt-M4/metapath/parse-metapath.xsl
+++ b/toolchains/xslt-M4/metapath/parse-metapath.xsl
@@ -91,6 +91,12 @@
 <!-- because the axis is expanded we switch the token   -->
     <xsl:template match="text()" mode="step-map"/>
     
+    <xsl:template match="XPath" mode="step-map">
+        <m:metapath>
+            <xsl:apply-templates mode="#current"/>
+        </m:metapath>
+    </xsl:template>
+    
     <xsl:template match="XPath/UnionExpr/UnaryExpr" mode="step-map">
         <m:alternative>
             <xsl:apply-templates mode="#current"/>
@@ -135,8 +141,6 @@
         </m:filter>
     </xsl:template>
     
-    
-    
     <xsl:template priority="2" match="Predicate/TOKEN" mode="step-map"/>
     
     <xsl:template match="Predicate/*" mode="step-map">
@@ -222,6 +226,13 @@
     <!-- Differences: text is not suppressed in step-map
            (slightly rewritten where paths are explicated)
       paths are kept, not only steps-->
+    
+    <xsl:template match="XPath" mode="path-map">
+        <m:metapath>
+            <xsl:apply-templates mode="#current"/>
+        </m:metapath>
+    </xsl:template>
+    
     <xsl:template match="XPath/UnionExpr/UnaryExpr" mode="path-map">
         <m:alternative>
             <xsl:apply-templates mode="#current"/>
diff --git a/toolchains/xslt-M4/testing/models_metaschema.xml b/toolchains/xslt-M4/testing/models_metaschema.xml
index c7863f1bb..9bbfa5157 100644
--- a/toolchains/xslt-M4/testing/models_metaschema.xml
+++ b/toolchains/xslt-M4/testing/models_metaschema.xml
@@ -74,7 +74,7 @@
                 <group-as name="groupable-assemblies"/>
             </assembly>
             <assembly ref="assembly-wrappable" max-occurs="unbounded">
-                <group-as name="wrapped-assemblies" in-xml="GROUPED"/>
+                <group-as name="wrapped-assemblies" in-xml="GROUPED" in-json="ARRAY"/>
             </assembly>
             <assembly ref="assembly-by-key" max-occurs="unbounded">
                 <group-as name="keyed-assemblies" in-json="BY_KEY"/>
@@ -195,10 +195,10 @@
         <description>assembly assembly-wrappable</description>
         <model>
             <field ref="field-wrappable" max-occurs="unbounded">
-                <group-as name="wrapped-fields" in-xml="GROUPED"/>
+                <group-as name="wrapped-fields" in-xml="GROUPED" in-json="ARRAY"/>
             </field>
             <assembly ref="assembly-wrappable" max-occurs="unbounded">
-                <group-as name="wrapped-assemblies" in-xml="GROUPED"/>
+                <group-as name="wrapped-assemblies" in-xml="GROUPED" in-json="ARRAY"/>
             </assembly>
         </model>
         
diff --git a/toolchains/xslt-M4/testing/test-xml-json-roundtrip.xpl b/toolchains/xslt-M4/testing/test-xml-json-roundtrip.xpl
new file mode 100644
index 000000000..6a37d32cb
--- /dev/null
+++ b/toolchains/xslt-M4/testing/test-xml-json-roundtrip.xpl
@@ -0,0 +1,202 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+  xmlns:c="http://www.w3.org/ns/xproc-step" version="1.0"
+  xmlns:metaschema="http://csrc.nist.gov/ns/metaschema/1.0"
+  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+  type="metaschema:test-roundtrip-conversions" name="test-roundtrip-conversions">
+  
+  <!-- &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& -->
+  <!-- Ports -->
+  
+  <p:input port="metaschema-source" primary="true"/>
+  <p:input port="testdata-xml"      primary="false"/>
+  <p:input port="parameters" kind="parameter"/>
+  
+  <p:serialization port="composed-metaschema" indent="true"/>
+  <p:output        port="composed-metaschema" primary="false">
+    <p:pipe        port="result"       step="metaschema-composed"/>
+  </p:output>
+  
+  <p:serialization port="definition-model" indent="true"/>
+  <p:output        port="definition-model" primary="false">
+    <p:pipe        port="result"           step="definition-map"/>
+  </p:output>
+  
+  <p:serialization port="e.xml-supermodel-conversion" indent="true"/>
+  <p:output        port="e.xml-supermodel-conversion" primary="false">
+    <p:pipe        port="result"               step="make-xml-converter"/>
+  </p:output>
+  
+  <p:serialization port="e.json-supermodel-conversion" indent="true"/>
+  <p:output        port="e.json-supermodel-conversion" primary="false">
+    <p:pipe        port="result"               step="make-json-converter"/>
+  </p:output>
+  
+  <p:serialization port="f_testdata-xml-source" indent="true"/>
+  <p:output        port="f_testdata-xml-source" primary="false">
+    <p:pipe        port="testdata-xml"           step="test-roundtrip-conversions"/>
+  </p:output>
+  
+  <p:serialization port="g_supermodel.1-is-from-xml-testdata" indent="true"/>
+  <p:output        port="g_supermodel.1-is-from-xml-testdata" primary="false">
+    <p:pipe        port="result"          step="convert-xml-testdata"/>
+  </p:output>
+  
+  <p:serialization port="h_MIDWAY_supermodel.1-as-xml" indent="true"/>
+  <p:output        port="h_MIDWAY_supermodel.1-as-xml" primary="false">
+    <p:pipe        port="result" step="convert-supermodel.1-to-xml"/>
+  </p:output>
+  
+  <p:serialization port="h_MIDWAY_supermodel.1-as-xpath-json" indent="true"/>
+  <p:output        port="h_MIDWAY_supermodel.1-as-xpath-json" primary="false">
+    <p:pipe        port="result"                step="convert-supermodel.1-to-json-xml"/>
+  </p:output>
+  
+  <p:serialization port="h_MIDWAY_supermodel.1-as-json" indent="true" method="text"/>
+  <p:output        port="h_MIDWAY_supermodel.1-as-json" primary="false">
+    <p:pipe        port="result"                step="serialize-supermodel.1-as-json"/>
+  </p:output>
+  
+  <p:serialization port="i_supermodel.2-is-from-MIDWAY-xpath-json" indent="true"/>
+  <p:output        port="i_supermodel.2-is-from-MIDWAY-xpath-json" primary="false">
+    <p:pipe        port="result" step="convert-jsonified-testdata"/>
+  </p:output>
+  
+  <!--<p:serialization port="k_json-from-supermodel.2" indent="true"/>
+  <p:output        port="k_json-from-supermodel.2" primary="false">
+    <p:pipe        port="result" step="convert-prose-to-markdown"/>
+  </p:output>-->
+  
+  <p:serialization port="k_xml-from-supermodel.2" indent="true"/>
+  <p:output        port="k_xml-from-supermodel.2" primary="false">
+    <p:pipe        port="result" step="convert-json-supermodel-to-xml"/>
+  </p:output>
+ 
+  <!-- &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& -->
+  <!-- Import (subpipeline) -->
+  
+  <p:import href="../metaschema-compose.xpl"/>
+  
+  <!-- &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& &&& -->
+  <!-- Pipeline -->
+  
+  <p:identity name="metaschema-source"/>
+  
+  <metaschema:metaschema-compose name="compose"/>
+  
+  <p:identity name="metaschema-composed"/>
+  
+  <!--<p:identity  name="make-model-map"/>-->
+  <p:xslt name="make-model-map">
+    <p:input port="stylesheet">
+      <p:document href="../compose/make-model-map.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:xslt name="unfold-model-map">
+    <p:input port="stylesheet">
+      <p:document href="../compose/unfold-model-map.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:xslt name="definition-map">
+    <p:input port="stylesheet">
+      <p:document href="../compose/reduce-map.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:xslt name="make-xml-converter">
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/produce-xml-converter.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:xslt name="convert-xml-testdata">
+    <p:input port="source">
+      <p:pipe port="testdata-xml" step="test-roundtrip-conversions"/>
+    </p:input>
+    <p:input port="stylesheet">
+      <p:pipe step="make-xml-converter" port="result"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:identity name="capture-supermodel.1"/>
+  
+  <!-- Now going back downhill to XML -->
+  <p:xslt name="convert-supermodel.1-to-xml">
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/supermodel-to-xml.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:sink/>
+  
+  <!-- Back downhill to JSON -->
+  
+  <!-- First, we markdownify the prose in the supermodel -->
+  <p:xslt name="convert-prose-to-markdown">
+    <p:input port="source">
+      <p:pipe port="result" step="convert-xml-testdata"/>
+    </p:input>
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/supermodel-to-markdown.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <!-- Now we map to XPath JSON -->
+  <p:xslt name="convert-supermodel.1-to-json-xml">
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/supermodel-to-json.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <!-- Finally we serialize to ensure JSONness -->
+  <!--<p:identity name="serialize-json"/>-->
+  <p:xslt name="serialize-supermodel.1-as-json">
+    <p:input port="stylesheet">
+      <p:document href="../lib/xpath-json-to-json.xsl"/>
+    </p:input>
+  </p:xslt>
+ 
+  <p:sink/>
+ 
+  <!-- Now to test the JSON to XML conversion - back around -->
+  
+  <!-- Producing the JSON to supermodel converter -->
+  <p:xslt name="make-json-converter">
+    <p:input port="source">
+      <p:pipe port="result" step="definition-map"/>
+    </p:input>
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/produce-json-converter.xsl"/>
+    </p:input>
+  </p:xslt>
+  
+  <p:sink/>
+  
+  <!-- Applying the JSON converter, from the serialized JSON we produce the supermodel again -->
+  <p:xslt name="convert-jsonified-testdata">
+    <p:input port="source">
+      <p:pipe port="result" step="convert-supermodel.1-to-json-xml"/>
+    </p:input>
+    <p:input port="stylesheet">
+      <p:pipe step="make-json-converter" port="result"/>
+    </p:input>
+  </p:xslt>
+  
+  <!-- Interpolating markup from the Markdown to produce a supermodel XML representation -->
+  <p:identity name="supermodel-markdown-to-markup"/>
+  <!--<p:xslt name="markup-supermodel-markdown">
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/markdown-to-supermodel.xsl"/>
+    </p:input>
+  </p:xslt>-->
+  
+  <!-- Go back down hill to XML -->
+  <p:xslt name="convert-json-supermodel-to-xml">
+    <p:input port="stylesheet">
+      <p:document href="../converter-gen/supermodel-to-xml.xsl"/>
+    </p:input>
+  </p:xslt>
+
+</p:declare-step>
\ No newline at end of file
diff --git a/toolchains/xslt-M4/validate/metaschema-check.sch b/toolchains/xslt-M4/validate/metaschema-check.sch
index a13a385a4..49ba97a1b 100644
--- a/toolchains/xslt-M4/validate/metaschema-check.sch
+++ b/toolchains/xslt-M4/validate/metaschema-check.sch
@@ -88,6 +88,7 @@
             <!--<sch:assert test="count(ancestor::m:model[1]//(m:field | m:define-field | m:assembly | m:define-assembly)[nm:identifiers(.)=$name]) = 1">group-as @name is not unique within this model</sch:assert>-->
             <!-- since definition-for-reference fails on an abstract metaschema we can't perform the json-key check there. -->
             <sch:assert test="$metaschema-is-abstract or not(@in-json='BY_KEY') or $def/m:json-key/@flag-name = $def/(m:flag/@ref|m:define-flag/@name)">Cannot group by key since the definition of <sch:value-of select="name(..)"/> '<sch:value-of select="../@ref"/>' has no json-key specified. Consider adding a json-key to the '<sch:value-of select="../@ref"/>' definition, or using a different 'in-json' setting.</sch:assert>
+            <sch:assert test="(@in-json='ARRAY') or not(@in-xml='GROUPED')">When @in-xml='GROUPED', @in-json must be 'ARRAY'.</sch:assert>
         </sch:rule>
         
         </sch:pattern>