The problem about IRI datatype.

Dear W3C Organization:
      I am a student. I study the SPARQL by myself recently. And I have a problem on the REGEX function.
      I want to know whether REGEX function can accept an IRI as its argument according to SPAQRL 1.0 specification.There are some example as follows:
      1.Regex(?x, "^abc", "i"); if ?x is mapping to an IRI. Whether the evaluation of Regex will produce an error? 


The definition of REGEX in W3C as follows:


xsd:boolean REGEX (string literal text, simple literal pattern)
 xsd:boolean  REGEX (string literal text, simple literal pattern, simple literal flags)   And we can see the arguments do not contain IRI datatype.  
 
    2.A < B; If A and B are both IRI.Whether the evaluation will produce an error?  Also for <=, >,>=.


The definition of '<' in W3C as follows:

      And we can also see the arguments do not contain IRI datatype.
      I looking forward your reply. Thank you very much! 


Regards
JiangShuo