Standard / DCAT (and profiles) export

core/src/main/java/org/fao/geonet/kernel/SchemaManager.java

@@ -76,6 +76,7 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 /**
  * Class that handles all functions relating to metadata schemas. This includes
@@ -106,6 +107,7 @@ public class SchemaManager {
     private static int activeWriters = 0;
     private Map<String, Schema> hmSchemas = new HashMap<>();
     private Map<String, Namespace> hmSchemasTypenames = new HashMap<>();
+    private Map<String, String> cswOutputSchemas = new HashMap<>();
     private String[] fnames = {"labels.xml", "codelists.xml", "strings.xml"};
     private Path schemaPluginsDir;
     private Path schemaPluginsCat;
@@ -958,6 +960,7 @@ private void addSchema(ApplicationContext applicationContext, Path schemaDir, El
 
         if (mds.getSchemaPlugin() != null && mds.getSchemaPlugin().getCswTypeNames() != null) {
             hmSchemasTypenames.putAll(mds.getSchemaPlugin().getCswTypeNames());
+            cswOutputSchemas.putAll(mds.getSchemaPlugin().getOutputSchemas());
         }
 
         // -- add cached xml files (schema codelists and label files)
@@ -1926,17 +1929,17 @@ public Map<String, Namespace> getHmSchemasTypenames() {
     }
 
     /**
-     * Return the list of namespace URI of all typenames declared in all schema plugins.
+     * Return the list of outputSchema declared in all schema plugins.
+     */
+    public Map<String, String> getOutputSchemas() {
+        return cswOutputSchemas;
+    }
+
+    /**
+     * Return the list of namespace URI of all outputSchema declared in all schema plugins.
      */
     public List<String> getListOfOutputSchemaURI() {
-        Iterator<String> iterator = hmSchemasTypenames.keySet().iterator();
-        List<String> listOfSchemaURI = new ArrayList<>();
-        while (iterator.hasNext()) {
-            String typeLocalName = iterator.next();
-            Namespace ns = hmSchemasTypenames.get(typeLocalName);
-            listOfSchemaURI.add(ns.getURI());
-        }
-        return listOfSchemaURI;
+        return new ArrayList<>(cswOutputSchemas.values());
     }
 
     /**

csw-server/src/main/java/org/fao/geonet/component/csw/GetCapabilities.java

@@ -65,6 +65,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import static org.fao.geonet.kernel.setting.SettingManager.isPortRequired;
 
@@ -529,6 +530,8 @@ private void setOperationsParameters(Element capabilities) {
      */
     private void populateTypeNameAndOutputSchema(Element op) {
         Map<String, Namespace> typenames = _schemaManager.getHmSchemasTypenames();
+        List<String> outputSchemas = _schemaManager.getOutputSchemas().values().stream().sorted().collect(Collectors.toList());
+
         List<Element> operations = op.getChildren("Parameter", Csw.NAMESPACE_OWS);
         for (Element operation : operations) {
             if ("typeNames".equals(operation.getAttributeValue("name"))) {
@@ -541,12 +544,10 @@ private void populateTypeNameAndOutputSchema(Element op) {
                         .setText(typename));
                 }
             } else if ("outputSchema".equals(operation.getAttributeValue("name"))) {
-                for (Map.Entry<String, Namespace> entry : typenames.entrySet()) {
-                    Namespace ns = entry.getValue();
-                    operation.addNamespaceDeclaration(ns);
+                outputSchemas.forEach(uri ->
                     operation.addContent(new Element("Value", Csw.NAMESPACE_OWS)
-                        .setText(ns.getURI()));
-                }
+                        .setText(uri))
+                );
             }
         }
     }

csw-server/src/main/java/org/fao/geonet/csw/common/OutputSchema.java

@@ -78,16 +78,16 @@ public static String parse(String schema, SchemaManager schemaManager) throws In
         if (schema.equals("csw:IsoRecord")) return "gmd";
         if (schema.equals("own")) return "own";
 
-        Map<String, Namespace> typenames = schemaManager.getHmSchemasTypenames();
-        for (Map.Entry<String, Namespace> entry : typenames.entrySet()) {
-            Namespace ns = entry.getValue();
-            if (schema.equals(ns.getURI())) {
-                return ns.getPrefix();
+        Map<String, String> typenames = schemaManager.getOutputSchemas();
+        for (Map.Entry<String, String> entry : typenames.entrySet()) {
+            String ns = entry.getValue();
+            if (schema.equals(ns)) {
+                return entry.getKey();
             }
         }
 
         throw new InvalidParameterValueEx("outputSchema",
-            String.format("'%s' schema is not valid. Supported values are %s",
+            String.format("'%s' output schema is not valid. Supported values are %s",
                 schema,
                 schemaManager.getListOfOutputSchemaURI().toString()));
     }

csw-server/src/main/java/org/fao/geonet/csw/common/util/Xml.java

@@ -125,22 +125,24 @@ public static Element applyElementSetName(ServiceContext context, SchemaManager
                                                ResultType resultType, String id, String displayLanguage) throws InvalidParameterValueEx {
         Path schemaDir = schemaManager.getSchemaCSWPresentDir(schema);
         Path styleSheet = schemaDir.resolve(outputSchema + "-" + elementSetName + ".xsl");
+        Path styleSheetWithoutElementSet = schemaDir.resolve(outputSchema + ".xsl");
 
-        if (!Files.exists(styleSheet)) {
+        if (!Files.exists(styleSheet) && !Files.exists(styleSheetWithoutElementSet)) {
             throw new InvalidParameterValueEx("OutputSchema",
                 String.format(
-                    "OutputSchema '%s' not supported for metadata with '%s' (%s).\nCorresponding XSL transformation '%s' does not exist for this schema.\nThe record will not be returned in response.",
-                    outputSchema, id, schema, styleSheet.getFileName()));
+                    "OutputSchema '%s' not supported for metadata with '%s' (%s).\nCorresponding XSL transformation '%s' (or '%s') does not exist for this schema.\nThe record will not be returned in response.",
+                    outputSchema, id, schema, styleSheet.getFileName(), styleSheetWithoutElementSet.getFileName()));
         } else {
             Map<String, Object> params = new HashMap<>();
             params.put("lang", displayLanguage);
 
+            Path xslFile = Files.exists(styleSheet) ? styleSheet : styleSheetWithoutElementSet;
             try {
-                result = org.fao.geonet.utils.Xml.transform(result, styleSheet, params);
+                result = org.fao.geonet.utils.Xml.transform(result, xslFile, params);
             } catch (Exception e) {
                 String msg = String.format(
-                    "Error occured while transforming metadata with id '%s' using '%s'.",
-                    id, styleSheet.getFileName());
+                    "Error occurred while transforming metadata with id '%s' using '%s'.",
+                    id, xslFile.getFileName());
                 context.error(msg);
                 context.error("  (C) StackTrace:\n" + Util.getStackTrace(e));
                 throw new InvalidParameterValueEx("OutputSchema", msg);

docs/manual/docs/api/rdf-dcat.md

@@ -1,24 +1,131 @@
-# RDF DCAT end point {#rdf-dcat}
+# DCAT {#rdf-dcat}
 
-!!! warning
+The catalogue has the capability to convert ISO to DCAT format in various API endpoint. [The first implementation of DCAT output was done in 2012](https://trac.osgeo.org/geonetwork/wiki/proposals/DCATandRDFServices) and was targeting interaction with semantic service and semantic sitemap support. DCAT output was available using a service named `rdf.search`. This service was deprecated in version 4.0.0 in favor of producing DCAT output in the [Catalog Service for the Web (CSW)](csw.md) or using the formatters API. 
 
-    Unavailable since version 4.0.0.
-
-    There is no known sponsor or interested party for implementing RDF DCAT.
-    Interested parties may contact the project team for guidance and to express their intent.
 
-The RDF DCAT end point provides a way of getting information about the catalog, the datasets and services, and links to distributed resources in a machine-readable format. The formats of the output are based on DCAT, an RDF vocabulary that is designed to facilitate interoperability between web-based data catalogs.
+## Supported DCAT profiles
 
-Reference:
+A base conversion is provided with complementary extensions for various profiles of DCAT developed in Europe:
 
-* [Data Catalog Vocabulary (DCAT)](https://www.w3.org/TR/vocab-dcat-3/)
+* a default DCAT export following W3C standard https://www.w3.org/TR/vocab-dcat-3/
+* an extension for the European DCAT-AP https://semiceu.github.io/DCAT-AP/releases/3.0.0/
+  * an extension for the European GeoDCAT-AP https://semiceu.github.io/GeoDCAT-AP/releases/
+  * an extension for the European DCAT-AP-Mobility https://mobilitydcat-ap.github.io/mobilityDCAT-AP/releases/1.0.0/index.html
+  * an extension for the European DCAT-AP-HVD https://semiceu.github.io/DCAT-AP/releases/2.2.0-hvd/
 
-## Upgrading from GeoNetwork 3.0 Guidance
+The mapping is done from ISO19115-3 to DCAT*. An ISO19139 to ISO19115-3 conversion can be applied before if needed.
 
-RDF DCAT API is no longer available.
+[The SEMICeu XSLT conversion](https://github.com/SEMICeu/iso-19139-to-dcat-ap/blob/master/iso-19139-to-dcat-ap.xsl)) is also included with minor improvements. This conversion is from ISO19139 to RDF and if needed a conversion from ISO19115-3 is applied.
 
-1. We recommend migrating to use of [Catalog Service for the Web (CSW)](csw.md) API to query and explore data.
+## Usage in the formatters API
 
-2. When downloading using `GetRecord` make use of the `application/rdf+xml; charset=UTF-8` output format.
-
-   This will allow retrieving records in the same document format as previously provided by RDF DCAT api.
+Each DCAT formats are available using a formatter eg. http://localhost:8080/geonetwork/srv/api/records/be44fe5a-65ca-4b70-9d29-ac5bf1f0ebc5/formatters/eu-dcat-ap?output=xml
+
+To add the formatter in the record view download list, the user interface configuration can be updated:
+
+![image](img/dcat-in-download-menu.png)
+
+```json
+{
+  "mods": {
+    "search": {
+      "downloadFormatter": [
+        {
+          "label": "exportMEF",
+          "url": "/formatters/zip?withRelated=false",
+          "class": "fa-file-zip-o"
+        },
+        {
+          "label": "exportPDF",
+          "url": "/formatters/xsl-view?output=pdf&language=${lang}",
+          "class": "fa-file-pdf-o"
+        },
+        {
+          "label": "exportXML",
+          "url": "/formatters/xml",
+          "class": "fa-file-code-o"
+        },
+        {
+          "label": "DCAT",
+          "url": "/formatters/dcat?output=xml"
+        },
+        {
+          "label": "EU-DCAT-AP",
+          "url": "/formatters/eu-dcat-ap?output=xml"
+        },
+        {
+          "label": "EU-GEO-DCAT-AP",
+          "url": "/formatters/eu-geodcat-ap?output=xml"
+        },
+        {
+          "label": "EU-DCAT-AP-MOBILITY",
+          "url": "/formatters/eu-dcat-ap-mobility?output=xml"
+        },
+        {
+          "label": "EU-DCAT-AP-HVD",
+          "url": "/formatters/eu-dcat-ap-hvd?output=xml"
+        }
+      ]
+```
+
+
+## Usage in the CSW service
+
+All DCAT profiles are also accessible using CSW protocol.
+
+A `GetRecordById` operation can be used: http://localhost:8080/geonetwork/srv/eng/csw?SERVICE=CSW&VERSION=2.0.2&REQUEST=GetRecordById&ID=da165110-88fd-11da-a88f-000d939bc5d8&outputSchema=https://semiceu.github.io/DCAT-AP/releases/2.2.0-hvd/ and is equivalent to the API http://localhost:8080/geonetwork/srv/api/records/da165110-88fd-11da-a88f-000d939bc5d8/formatters/eu-dcat-ap-hvd?output=xml.
+
+A `GetRecords` operation can be used to retrieve a set of records: http://localhost:8080/geonetwork/srv/fre/csw?SERVICE=CSW&VERSION=2.0.2&REQUEST=GetRecords&outputSchema=http://data.europa.eu/930/&elementSetName=full&resultType=results&maxRecords=300
+
+Use the `outputSchema` parameter to select the DCAT profile to use. The following values are supported:
+
+```xml
+<ows:Parameter name="outputSchema">
+   <ows:Value>http://data.europa.eu/930/</ows:Value>
+   <ows:Value>http://data.europa.eu/930/#semiceu</ows:Value>
+   <ows:Value>http://data.europa.eu/r5r/</ows:Value>
+   <ows:Value>http://standards.iso.org/iso/19115/-3/mdb/2.0</ows:Value>
+   <ows:Value>http://www.isotc211.org/2005/gfc</ows:Value>
+   <ows:Value>http://www.isotc211.org/2005/gmd</ows:Value>
+   <ows:Value>http://www.opengis.net/cat/csw/2.0.2</ows:Value>
+   <ows:Value>http://www.w3.org/ns/dcat#</ows:Value>
+   <ows:Value>http://www.w3.org/ns/dcat#core</ows:Value>
+   <ows:Value>https://semiceu.github.io/DCAT-AP/releases/2.2.0-hvd/</ows:Value>
+   <ows:Value>https://w3id.org/mobilitydcat-ap</ows:Value>
+```
+
+Those values are listed in the `GetCapabilities` operation http://localhost:8080/geonetwork/srv/eng/csw?SERVICE=CSW&VERSION=2.0.2&REQUEST=GetCapabilities.
+
+## Usage in OGC API Records
+
+For the time being, OGC API Records provides a simplified DCAT output (based on the index document). 
+
+## DCAT validation
+
+The DCAT validation can be done using online validation tool:
+* https://www.itb.ec.europa.eu/shacl/dcat-ap/upload
+
+Depending on the target DCAT profile to use, it may be required to build proper ISO template and metadata record containing all required fields. Usually profiles are adding constraints for usage of specific vocabularies and fields (eg. [for High Value datasets, specific vocabularies are defined for categories, license, applicable legislations, ...](https://semiceu.github.io/DCAT-AP/releases/2.2.0-hvd/#controlled-vocabularies-to-be-used)).
+
+
+## Mapping considerations
+
+The mapping is done from ISO19115-3 to DCAT. The mapping may not cover all usages and may be adapted. This can be done in the `iso19115-3.2018` schema plugin in the `formatter/dcat*` XSLT files.
+
+Some points under discussion are:
+* Object vs Reference: 
+  * Should we use object or reference for some fields (eg. contact, organisation, ...)?
+  * What should be the reference URI?
+  * Where is defined the reference URI in ISO?
+
+eg. for an organisation, the URI will be the first value in the following sequence:
+```xml
+(cit:partyIdentifier/*/mcc:code/*/text(),
+cit:contactInfo/*/cit:onlineResource/*/cit:linkage/gco:CharacterString/text(),
+cit:name/gcx:Anchor/@xlink:href,
+@uuid)[1]
+```
+
+* No equivalent field in ISO (eg. Where to store `spdx:checksum` in ISO?)
+
+* Associated resources: Links between are not always bidirectional so using the associated API would allow to populate more relations. This is also mitigated with the complete RDF graph of the catalogue is retrieved providing relations from all records.

pom.xml

@@ -469,7 +469,7 @@
         <groupId>org.apache.jena</groupId>
         <artifactId>apache-jena-libs</artifactId>
         <type>pom</type>
-        <version>3.17.0</version>
+        <version>4.10.0</version>
       </dependency>
 
       <!-- PDF stuff: Managed by Mapfish -->
@@ -554,6 +554,11 @@
         <artifactId>commons-email</artifactId>
         <version>1.5</version>
       </dependency>
+      <dependency>
+        <groupId>commons-codec</groupId>
+        <artifactId>commons-codec</artifactId>
+        <version>1.15</version>
+      </dependency>
       <dependency>
         <groupId>org.apache.xmlgraphics</groupId>
         <artifactId>xmlgraphics-commons</artifactId>

schemas/iso19110/src/main/resources/config-spring-geonetwork.xml

@@ -31,6 +31,12 @@
 
   <bean id="iso19110SchemaPlugin"
         class="org.fao.geonet.schema.iso19110.ISO19110SchemaPlugin">
+    <property name="outputSchemas">
+      <util:map key-type="java.lang.String" value-type="java.lang.String">
+        <entry key="csw" value="http://www.opengis.net/cat/csw/2.0.2"/>
+        <entry key="gfc" value="http://www.isotc211.org/2005/gfc"/>
+      </util:map>
+    </property>
     <property name="xpathTitle">
       <util:list value-type="java.lang.String">
         <value>gmx:name/gco:CharacterString</value>

schemas/iso19115-3.2018/src/main/plugin/iso19115-3.2018/convert/ISO19139/fromISO19139.xsl

@@ -98,7 +98,7 @@
     <xsl:variable name="stylesheetVersion" select="'0.1'"/>
 
 
-    <xsl:template match="/">
+    <xsl:template match="/" name="to-iso19115-3">
         <!--
         root element (MD_Metadata or MI_Metadata)
         -->

schemas/iso19115-3.2018/src/main/plugin/iso19115-3.2018/formatter/dcat/dcat-commons.xsl

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xsl:stylesheet version="2.0"
+                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+                xmlns:xs="http://www.w3.org/2001/XMLSchema"
+                xmlns:locn="http://www.w3.org/ns/locn#"
+                xmlns:dcat="http://www.w3.org/ns/dcat#"
+                exclude-result-prefixes="#all">
+
+  <xsl:output method="xml"
+              indent="yes"
+              encoding="utf-8"
+              cdata-section-elements="locn:geometry dcat:bbox"/>
+
+  <xsl:template name="create-namespaces">
+    <xsl:namespace name="rdf" select="'http://www.w3.org/1999/02/22-rdf-syntax-ns#'"/>
+    <xsl:namespace name="rdfs" select="'http://www.w3.org/2000/01/rdf-schema#'"/>
+    <xsl:namespace name="owl" select="'http://www.w3.org/2002/07/owl#'"/>
+    <xsl:namespace name="dct" select="'http://purl.org/dc/terms/'"/>
+    <xsl:namespace name="dcat" select="'http://www.w3.org/ns/dcat#'"/>
+    <xsl:namespace name="foaf" select="'http://xmlns.com/foaf/0.1/'"/>
+    <xsl:namespace name="vcard" select="'http://www.w3.org/2006/vcard/ns#'"/>
+    <xsl:namespace name="prov" select="'http://www.w3.org/ns/prov#'"/>
+    <xsl:namespace name="org" select="'http://www.w3.org/ns/org#'"/>
+    <xsl:namespace name="pav" select="'http://purl.org/pav/'"/>
+    <xsl:namespace name="adms" select="'http://www.w3.org/ns/adms#'"/>
+    <xsl:namespace name="skos" select="'http://www.w3.org/2004/02/skos/core#'"/>
+  </xsl:template>
+</xsl:stylesheet>