I would like my Eclipse plug-in to specify a XSD file to Eclipse so it can be added to the catalog.
The org.eclipse.wst.xml.core.catalogContributions
extension point lets you add to the catalog (this requires that you have the Web Tools (WST) component of Eclipse installed).
For example the org.eclipse.wst.xsd.core
plugin adds this:
<extension
point="org.eclipse.wst.xml.core.catalogContributions">
<catalogContribution id="default">
<uri
name="http://www.w3.org/2001/XMLSchema"
uri="platform:/plugin/org.eclipse.xsd/cache/www.w3.org/2001/XMLSchema.xsd" />
<system
systemId="http://www.w3.org/2001/xml.xsd"
uri="platform:/plugin/org.eclipse.xsd/cache/www.w3.org/2001/xml.xsd"/>
</catalogContribution>
</extension>