Re: N3 rules: literals as subject and object in built-in functions

To clarify my question, in RDF syntax:
http://www.w3.org/TR/rdf-syntax-grammar/#section-Syntax-intro
it says "RDF literals, which can only be object nodes, become either XML
element text content or XML attribute values."
So, is the restriction that only object nodes can be literals merely
a limitation of the XML representation?  (If so, a good reason to get
away from XML....)

Jeff Thompson wrote:
> 
> http://www.w3.org/2004/12/rules-ws/paper/94/
> In "Experience with N3 rules", it says built-in functions "are simply 
> represented as RDF properties",
> and gives the example:
>   { ex:d test:point ?x.  ?x math:sin ?y } =>  {...}
> 
> Presumably ?x and ?y for math:sin would be a number literal.  But an RDF 
> graph only
> allows the object to be a literal, not a subject.
> 1. Am I right that RDF does not allow the subject of a triple to be a 
> literal?
> 2. If so, how can a math built-in function that uses literals be the 
> predicate of an RDF triple?
> 
> Thanks,
> - Jeff
> 
> 
> 
> 
>