Sure, that's what the <include> element is for. Most xwork.xml files
already have one:

<xwork>
    <include file="webwork-default.xml"/>
    <include file="config-browser.xml"/>
    <package name="default" extends="webwork-default">
....
    </package>
    <include file="other.xml"/>
</xwork>

This tells it to load the webwork-default.xml from the webwork jar file
to get all of those interceptor and result definitions.

You can put your own <include> in your xwork.xml interchangeably with
<package> elements... They will be loaded in the same order as it reads
from top to bottom and adds things as it reads them.

@see com.opensymphony.xwork.config.ConfigurationManager
@see com.opensymphony.xwork.config.Configuration
@see com.opensymphony.xwork.config.impl.DefaultConfiguration
@see com.opensymphony.xwork.config.ConfigurationProvider
@see com.opensymphony.xwork.config.providers.XmlConfigurationProvider