Metadata Conversion (XSLT)

The convert directory contains XSLT (Extensible Stylesheet Language Transformation) files that enable conversion of metadata records from one schema to another or to different formats. This component is essential for metadata interoperability and data exchange.

Overview

Purpose

Convert metadata records between different schemas
Support multiple output formats (ISO19115/19139, Dublin Core, ANDS RIFCS, etc.)
Support schema version migrations
Facilitate data exchange with external systems
Provide fallback conversions to base standards

XSLT Technology

XSLT is a W3C standard language for transforming XML documents. It provides powerful mechanisms for:

Mapping element structures between schemas
Reformatting and restructuring metadata
Filtering and selecting relevant content
Creating derived schemas from base schemas

Directory Structure

File Organization

schema-name/
├── schema-conversions.xml (configuration file - at root level)
├── convert/ (mandatory directory for XSLT files)
│   ├── iso19139.mcp.xsl (profile-specific conversion)
│   ├── iso19139.mcp-1.4.xsl (version-specific conversion)
│   ├── oai_dc.xsl (Dublin Core output)
│   ├── rif.xsl (ANDS RIFCS format)
│   ├── to19139.xsl (base ISO19115/19139)
│   └── other-format.xsl (additional conversions)
└── [other schema components]

Important Notes on Modern GeoNetwork

In modern GeoNetwork versions (4.x):

The configuration file is named schema-conversions.xml (not convert.xml)
It is located at the root level of the schema plugin directory (not inside convert/)
The convert/ directory is mandatory in all schema plugins
All XSLT files are stored within the convert/ subdirectory

Naming Conventions

<target>-<format>.xsl or similar descriptive naming for XSLT files
Examples: oai_dc.xsl, iso19139.xsl, dcat.xsl, fromISO19139.xsl

Schema-Conversions.xml Configuration File

The schema-conversions.xml file defines all available conversions and their metadata. It is located at the schema plugin root level.

Structure

<?xml version="1.0" encoding="UTF-8"?>
<conversions>
  <converter 
    name="xml_iso19139.mcp"
    nsUri="http://bluenet3.antcrc.utas.edu.au/mcp" 
    schemaLocation="http://bluenet3.antcrc.utas.edu.au/mcp-1.5-experimental/schema.xsd" 
    xslt="iso19139.mcp.xsl" 
  />
  <converter 
    name="xml_iso19139.mcpTooai_dc"
    nsUri="http://www.openarchives.org/OAI/2.0/" 
    schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc.xsd" 
    xslt="oai_dc.xsl" 
  />
</conversions>

Modern GeoNetwork Implementation

Important: In modern GeoNetwork versions (4.x):

The configuration file is schema-conversions.xml located at the schema root level
Previous versions used convert.xml inside the convert/ directory, but this is no longer the standard approach
The file is automatically discovered by GeoNetwork’s SchemaManager
All XSLT files must be in the convert/ subdirectory
The convert/ directory is mandatory even if conversions are minimal

Converter Attributes

`name` Attribute

Unique identifier for this conversion
Used internally by GeoNetwork to reference the conversion
Convention: Use xml_<source>To<target> format (e.g., xml_iso19139mcpTooai_dc)
The xml_ prefix identifies this as an XML-to-XML transformation service
Example: xml_iso19139.mcp, xml_iso19139.mcpTooai_dc, xml_iso19139.mcpToRIFCS

`nsUri` Attribute

Namespace URI: The primary XML namespace of the output format
Identifies the schema/format produced by this conversion
Used for schema detection and validation
Examples:
- http://www.isotc211.org/2005/gmd (ISO19115/19139)
- http://www.openarchives.org/OAI/2.0/ (Dublin Core via OAI-PMH)
- http://ands.org.au/standards/rif-cs/registryObjects (ANDS RIFCS)

`schemaLocation` Attribute

URL of the XML Schema Definition (XSD) for the output format
Tells validating parsers where to find the schema
Should point to the authoritative schema location
Added to output XML documents for validation purposes
Examples:
- Official standards URLs: http://www.isotc211.org/2005/gmd/gmd.xsd
- External service URLs: http://www.openarchives.org/OAI/2.0/oai_dc.xsd

`xslt` Attribute

Filename of the XSLT stylesheet that performs the conversion
Located in the convert/ directory
Path is relative to the convert.xml file
Examples: iso19139.mcp.xsl, oai_dc.xsl, rif.xsl

Complete Example

<?xml version="1.0" encoding="UTF-8"?>
<conversions>
  <!-- Convert to this schema itself (with updated schemaLocation) -->
  <converter 
    name="xml_iso19139.mcp"
    nsUri="http://bluenet3.antcrc.utas.edu.au/mcp" 
    schemaLocation="http://bluenet3.antcrc.utas.edu.au/mcp-1.5-experimental/schema.xsd" 
    xslt="iso19139.mcp.xsl" 
  />

  <!-- Convert to MCP version 1.4 (removes experimental 1.5 elements) -->
  <converter 
    name="xml_iso19139.mcp-1.4"
    nsUri="http://bluenet3.antcrc.utas.edu.au/mcp" 
    schemaLocation="http://bluenet3.antcrc.utas.edu.au/mcp/schema.xsd" 
    xslt="iso19139.mcp-1.4.xsl" 
  />

  <!-- Convert to OAI Dublin Core format for harvesting -->
  <converter 
    name="xml_iso19139.mcpTooai_dc"
    nsUri="http://www.openarchives.org/OAI/2.0/" 
    schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc.xsd" 
    xslt="oai_dc.xsl" 
  />

  <!-- Convert to ANDS RIFCS format (Australian National Data Service) -->
  <converter 
    name="xml_iso19139.mcpToRIFCS"
    nsUri="http://ands.org.au/standards/rif-cs/registryObjects" 
    schemaLocation="http://services.ands.org.au/home/orca/schemata/registryObjects.xsd" 
    xslt="rif.xsl" 
  />

  <!-- Convert to base ISO19115/19139 (remove profile-specific elements) -->
  <converter 
    name="xml_iso19139"
    nsUri="http://www.isotc211.org/2005/gmd" 
    schemaLocation="http://www.isotc211.org/2005/gmd/gmd.xsd" 
    xslt="to19139.xsl" 
  />
</conversions>

XSLT Stylesheet Basics

Purpose of Conversion XSLTs

Map source metadata elements to target schema elements
Transform XML structure and namespace
Handle incompatible data models
Filter unwanted or incompatible content
Apply business logic for format-specific requirements

Basic XSLT Structure

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:gmd="http://www.isotc211.org/2005/gmd"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  exclude-result-prefixes="gmd">

  <!-- Match the root element -->
  <xsl:template match="/gmd:MD_Metadata">
    <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
             xmlns:dc="http://purl.org/dc/elements/1.1/">
      <!-- Transform metadata to target format -->
      <rdf:Description rdf:about="...">
        <dc:title>
          <xsl:value-of select="gmd:hierarchyLevel/..."/>
        </dc:title>
      </rdf:Description>
    </rdf:RDF>
  </xsl:template>

</xsl:stylesheet>

Common XSLT Elements

<xsl:template>: Defines transformation rules for matched elements
<xsl:value-of>: Extracts and outputs text values
<xsl:for-each>: Iterates over element collections
<xsl:if> / <xsl:choose>: Conditional logic
<xsl:apply-templates>: Applies templates recursively

Common Conversion Scenarios

1. Profile to Base Schema Conversion

Remove profile-specific elements and convert to base ISO19115/19139:

<!-- Remove profile elements, keep only base ISO elements -->
<xsl:template match="mcp:revisionDate"/>

2. Version Migration

Convert between different versions of the same schema:

Remove deprecated elements
Map old element names to new names
Add default values for new mandatory elements

3. Format Conversion (OAI-PMH)

Convert to Dublin Core for metadata harvesting:

<dc:title><xsl:value-of select="gmd:title"/></dc:title>
<dc:description><xsl:value-of select="gmd:abstract"/></dc:description>
<dc:creator><xsl:value-of select="gmd:pointOfContact/*/gmd:individualName"/></dc:creator>

4. System-Specific Format

Convert to formats required by other systems (ANDS RIFCS, CSW, etc.)

Best Practices

Define Core Conversions: Include conversions to base schema and common formats (Dublin Core)
Namespace Accuracy: Ensure correct namespace URIs in convert.xml
Schema Validation: Test output against target schema definitions
Lossless Design: When possible, preserve metadata during conversion
Documentation: Document mapping logic and assumptions in XSLT comments
Error Handling: Include templates for unexpected elements (identity templates)
Performance: Optimize XSLT for large metadata records
Testing: Validate conversions with real-world metadata samples

Metadata Conversion (XSLT)

Overview

Purpose

XSLT Technology

Directory Structure

File Organization

Important Notes on Modern GeoNetwork

Naming Conventions

Schema-Conversions.xml Configuration File

Structure

Modern GeoNetwork Implementation

Converter Attributes

`name` Attribute

`nsUri` Attribute

`schemaLocation` Attribute

`xslt` Attribute

Complete Example

XSLT Stylesheet Basics

Purpose of Conversion XSLTs

Basic XSLT Structure

Common XSLT Elements

Common Conversion Scenarios

1. Profile to Base Schema Conversion

2. Version Migration

3. Format Conversion (OAI-PMH)

4. System-Specific Format

Best Practices

Example Conversion Use Cases

Interoperability

Migration

Harvesting

References

Overview

Purpose

XSLT Technology

Directory Structure

File Organization

Important Notes on Modern GeoNetwork

Naming Conventions

Schema-Conversions.xml Configuration File

Structure

Modern GeoNetwork Implementation

Converter Attributes

name Attribute

nsUri Attribute

schemaLocation Attribute

xslt Attribute

Complete Example

XSLT Stylesheet Basics

Purpose of Conversion XSLTs

Basic XSLT Structure

Common XSLT Elements

Common Conversion Scenarios

1. Profile to Base Schema Conversion

2. Version Migration

3. Format Conversion (OAI-PMH)

4. System-Specific Format

Best Practices

Example Conversion Use Cases

Interoperability

Migration

Harvesting

References

`name` Attribute

`nsUri` Attribute

`schemaLocation` Attribute

`xslt` Attribute