Compiled UIC source code (Geoworks UI Compiler)
GEOS has been known as PC/GEOS, Ensemble, then NewDeal Ensemble, and is now Breadbox Ensemble.
The RDF file extension is also associated with the Research Document information Format and the Resource Description Framework file format (related to XML and metadata).
Learn more about RDF files:
Wikipedia has an entry on GEOS.
See user interface FAQs at IT Knowledge Exchange.