Thesaurus / OWL format / Mobility theme hierarchy

Follow up of #7674


Mobility DCAT theme vocabulary top concepts is available at
https://mobilitydcat-ap.github.io/controlled-vocabularies/mobility-theme/latest/index.html#/

The vocabulary contains 2 top concepts:

```xml
<skos:hasTopConcept rdf:resource="https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-category"/>
<skos:hasTopConcept rdf:resource="https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-sub-category"/>
```
which are not really needed for browsing the main categories and sub categories.

Use the narrower terms of the "content category" top concept as the top concepts of the scheme
to facilitate keyword selection in editor and generate proper facet hierarchy in search.

web/src/main/webapp/xslt/services/thesaurus/owl-to-skos.xsl

@@ -24,9 +24,9 @@
 <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                 xmlns:owl="http://www.w3.org/2002/07/owl#"
                 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
-                xmlns:dc="http://purl.org/dc/elements/1.1/"
-                xmlns:dcterms="http://purl.org/dc/terms/"
+                xmlns:terms="http://purl.org/dc/terms/"
                 xmlns:skos="http://www.w3.org/2004/02/skos/core#"
+                xmlns:xs="http://www.w3.org/2001/XMLSchema"
                 exclude-result-prefixes="#all"
                 version="2.0">
 
@@ -40,23 +40,68 @@
 
   <xsl:template mode="owl-to-skos"
                 match="owl:Ontology">
-    <rdf:RDF xmlns:skos="http://www.w3.org/2004/02/skos/core#"
-             xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
-             xmlns:dc="http://purl.org/dc/elements/1.1/"
-             xmlns:dcterms="http://purl.org/dc/terms/">
+    <rdf:RDF>
+      <xsl:namespace name="skos" select="'http://www.w3.org/2004/02/skos/core#'"/>
+      <xsl:namespace name="rdf" select="'http://www.w3.org/1999/02/22-rdf-syntax-ns#'"/>
+      <xsl:namespace name="dc" select="'http://purl.org/dc/elements/1.1/'"/>
+      <xsl:namespace name="terms" select="'http://purl.org/dc/terms/'"/>
       <skos:ConceptScheme rdf:about="{@rdf:about}">
-        <xsl:copy-of select="dcterms:*|skos:*"/>
+        <xsl:copy-of select="terms:*|skos:*[local-name() != 'hasTopConcept']" copy-namespaces="no"/>
+
+        <!--
+        Custom case for Mobility DCAT theme vocabulary top concepts.
+        https://mobilitydcat-ap.github.io/controlled-vocabularies/mobility-theme/latest/index.html#/
+
+        The vocabulary contains 2 top concepts:
+        <skos:hasTopConcept rdf:resource="https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-category"/>
+        <skos:hasTopConcept rdf:resource="https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-sub-category"/>
+        which are not really needed for browsing the main categories and sub categories.
+
+        Use the narrower terms of the "content category" top concept as the top concepts of the scheme
+        to facilitate keyword selection in editor and generate proper facet hierarchy in search.
+        -->
+        <xsl:variable name="mobilityThemeTopConcept"
+                      select="../owl:NamedIndividual[@rdf:about = 'https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-category']"/>
+        <xsl:choose>
+          <xsl:when test="$mobilityThemeTopConcept">
+            <xsl:for-each select="$mobilityThemeTopConcept/skos:narrower">
+              <skos:hasTopConcept rdf:resource="{@rdf:resource}"/>
+            </xsl:for-each>
+          </xsl:when>
+          <xsl:otherwise>
+            <xsl:copy-of select="skos:hasTopConcept" copy-namespaces="no"/>
+          </xsl:otherwise>
+        </xsl:choose>
       </skos:ConceptScheme>
 
       <xsl:apply-templates mode="owl-to-skos"
                            select="../owl:NamedIndividual[skos:prefLabel]"/>
     </rdf:RDF>
   </xsl:template>
 
+  <xsl:variable name="excludedConcepts"
+                select="(
+                'https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-category',
+                'https://w3id.org/mobilitydcat-ap/mobility-theme/data-content-sub-category'
+                )"
+                as="xs:string*"/>
+
+  <xsl:template mode="owl-to-skos"
+                match="owl:NamedIndividual[@rdf:about = $excludedConcepts]
+                            |skos:broader[@rdf:resource = $excludedConcepts]"/>
+
   <xsl:template mode="owl-to-skos"
                 match="owl:NamedIndividual">
     <skos:Concept rdf:about="{@rdf:about}">
-      <xsl:copy-of select="skos:*"/>
+      <xsl:apply-templates mode="owl-to-skos" select="skos:*"/>
     </skos:Concept>
   </xsl:template>
+
+  <xsl:template mode="owl-to-skos"
+                match="@*|node()">
+    <xsl:copy copy-namespaces="no">
+      <xsl:apply-templates select="@*|node()" mode="owl-to-skos"/>
+    </xsl:copy>
+  </xsl:template>
+
 </xsl:stylesheet>