The default namespace of RIF is http://www.w3.org/2007/rif#.
The abstract syntax of RIF Core is specified in asn06 as follows:
It is visualized by a UML diagram as follows:
Automatic asn06-to-UML transformation has been employed for this, using the available tool.
The concrete syntax, in particular an XML Schema, will be derived from this (to follow in a later Working Draft).