There are two ways how create virtual database. You can deploy *.vdb file which is basically zip archive with changed extension, or deploy just vdb.xml file. The second way doesn't work through soa admin console web interface.

Error message:
Failed to create Resource weather-vdb.xml - cause: Incorrect extension specified on filename

How to reproduce:
In soa web interface log in to Admin Console, than open "Virtual Database (VDB)s" link, than click "Add a new resource" button, and try to upload weather-vdb.xml which is attached.

Workaround:
Just copy weather-vdb.xml to the deploy folder.

weather-vdb.xml and weather-ds.xml which is required if you want to deploy vdb in active state are attached.