According to the ​documentation of Relax NG, there is no way of telling a document the location of the Relax NG Schema as it is possible with a DTD. As our main editor at the moment is oxygen, either a processing instruction has to be entered into the xml-file, or a validation scenario has to be entered into oxygen (via Dokument > Validieren > Konfiguriere Validierungsszenario).

In order to keep things clean and not confuse the user with relative paths to a local copy, a link to the Relax NG schema on this server can be entered. However, as this server can be reached only via https, oxygen itself has to be configured to accept a secure connection.

For this purpose, the certificate of the it-dev server has to be downloaded and stored in the keychain (when on Mac OS). Then, edit oxygen's Info.plist and add

			<key>javax.net.ssl.trustStoreProvider</key>
			<string>Apple</string>
			<key>javax.net.ssl.trustStoreType</key>
			<string>KeychainStore</string>

under Java > Properties.

The link to the latest version of the schema root is https://it-dev.mpiwg-berlin.mpg.de/svn/mpdl-project-content/trunk/schema/echo/echo.rnc