In Notation3, the words 'true' and 'false' represent values of the
primitive data type xsd:boolean, whereas in Ripple, they are relational
primitives which consume arguments and produce results (they're identical
to stack:pop and stack:popd). While this is elegant, it's also a little
confusing, because Ripple's text syntax is based on Notation3. Let 'true'
and 'false' be simple values as in Notation3, and leave control flow to
the remaining logic primitives.
Original link: http://code.google.com/p/ripple/issues/detail?id=23