The OC4J web module supports setting a virtual directory. The virtual directory allows a web module to serve content from a physical directory outside of the actual deployed web module.
In the orion-web.xml file the tag is of this form:
<virtual-directory virtual-path="/bar" real-path="D:\static_content\bar" />
Which means that when the web module is deployed it can serve content directly from the self contained WAR file (and its sub-directories) via the URL of /foo.
But it also means that the web module can now also serve content from the directory specified as the real-path attribute via the URL of /foo/bar.
You can specify this virtual-directory setting using an embedded orion-web.xml in which it is already set OR with the OC4J 10.1.3 release you can use the funky Deployment Plan Editor to specify it at deployment time.
This can be handy for example when you have web modules which need to serve content which is being periodically generated by other services such as a report engine (or graphic designers updating HTML or images) but don't want to lump the content into the exploded directory of the web module.