Plugin Metadata Schemas and Profiles

Date	2010/09/07
Contact(s)	Simon Pigot
Last edited	2010/10/26
Status	Completed and committed to trunk 2.7.x, documentation attached to this proposal has been replaced with a section in the developers manual (cd docs/eng/developer; make html)
Assigned to release	2.7.x
Resources	Available

Overview

It should be possible to plug-in Metadata Schemas (including profiles). This means that a user/admin should be able to use a service to add a profile/schema to their existing GeoNetwork installation without having to make manual changes to config, Java code, xslts and javascript.

Proposal Type

• Type: Core Change
• App: GeoNetwork
• Module: Kernel, Data Manager

Links

• Documents:
• Email discussions:
• Other wiki discussions:

Voting History

• Proposed on 8/12/10, Passed with +1 from Jeroen, Mathieu, Francois, Emanuele, Patrizia

Motivations

To add a schema to GeoNetwork a user currently has to:

• add the schema and ancillaries to web/geonetwork/xml/schemas directory
• add codelists and labels xml files to web/geonetwork/WEB-INF/config.xml
• add presentation xslts to web/geonetwork/xsl and import them into web/geonetwork/xsl/metadata-utils.xsl
• modify web/geonetwork/xsl/{metadata.xsl,metadata-utils.xsl} to switch on schema for full and brief mode processing
• add brief, summary and full presentation xslts to web/geonetwork/xml/csw/schemas
• add schema detection code to the autodetectSchema method in DataManager.java
• add namespaces used for elements to the tooltip javascript (web/geonetwork/scripts/editor/tooltip.js and web/geonetwork/scripts/editor/simpletooltip.js)
• schemas added to GeoNetwork exist inside the web application deployment making it more difficult to manage upgrades and new deployments of GeoNetwork

This is not only tedious but requires a fair bit of knowledge to ensure that the installation is not broken by inappropriate or incorrect changes. In some cases these changes are large enough that communities with national schemas/profiles will create their own branch of GeoNetwork to support their schema/profile. This should not be necessary.

Removing the need to make code changes and consolidating schema information will make adding a schema to GeoNetwork much easier. Having plug in schemas/profiles will also remove the need to create a code branch to support the schema/profile.

Proposal

Make the following changes:

• consolidate presentation xslts into the schema directory
• remove the need for switch on schema type in metadata.xsl and metadata-utils.xsl
• provide the ability to rewrite xslt imports using a URI resolver and oasis catalog file
• allow users to rewrite schemaLocation hints using an oasis catalog file/files
• add a SchemaManager class to encapsulate and provide schema information to other classes in GeoNetwork
• rewrite the Info service so that it no longer requires the namespace URI to be provided by the tooltip requests (will use SchemaManager to get this info instead)
• change schema autodetection code to use information from the SchemaManager (we use some code and ideas from the enhanced schema autodetect approach developed by Dominic Owen of USGIN and some enhancements). Basically schemas can be detected using the root element of a metadata document or some elements and values in the metadata document (eg. metadata standard name and version) or by looking for an element with a specific namespace
• move codelist and label xml file caching for schemas from Jeeves guiservices to GeoNetwork guiservices - no longer necessary to add these files to the gui section of web/geonetwork/WEB-INF/config.xml
• Add localized strings support for strings that may be used in the presentation xslts - no longer necessary to add these to the gui section of .....
• move templates and sample-data into schema directory and change gast and other code to use the SchemaManager to obtain paths to these directories
• add services that accept a schema zip file directly or URL of a schema zip file or UUID of a metadata record with schema zip archive attached, which retrieve and unpack the schema from the zip file into the schemaPlugins directory, and adds the schema to the list of schemas that GeoNetwork knows about (no config changes required) - add, delete and update

• Metadata schemas and profiles can also be bundled up as installer packs. The following is a snapshot of the installer with some schemas/profiles as optional installer packs:

Backwards Compatibility Issues

• Those installations with their own schemas and profiles will need to recast them into the plugin format - this means moving common strings and presentation xslts etc to the schema directory

New libraries added

xml-commons-resolver 1.2 - Apache lib to support resolving various XML entities and URIs using oasis catalogs

Risks

None known

Participants

• Simon Pigot
• Dominic Owen, USGIN - ideas and first version of schema autodetect code (since refined)
• Francois Prunayre - tested the French Profile
• Other members of the GeoNetwork community. In Australia: Craig Jones - IMOS/eMii, John Hockaday - OSDM, Xiangtan Lin - CSIRO, Yarralumla