- From: Stijn Vansummeren <stijn.vansummeren@luc.ac.be>
- Date: Thu, 20 Nov 2003 17:42:42 +0100
- To: www-ql@w3.org

I have a question concerning the typing of literals and its interaction with type annotations (for instance in let expressions) in the formal semantics. The static rule for integer literals is -------------------------------------------------- statenv |- integerLiteral : xs:integer Now suppose we have the following type definition: define type feet restricts xs:integer Is the following expression well-typed? let $x as feet := 15 return $x I believe it is not, since the literal 15 is given the type xs:integer by the literal typing rule above. The typing rule for let specifies that "xs:integer" should be a subtype of "feet". By definition, "xs:integer" is a subtype of type "feet" iff every value that matches "xs:integer" also matches "feet". However, the value "15 of type xs:integer" will not match type "feet", since there is only one matching rule for atomic values: statEnv |- AtomicTypeName1 derives from AtomicTypeName2 ------------------------------------------------------------------------------------------------------ statEnv |- AtomicValue of type AtomicTypeName1 matches AtomicTypeName2 In our case, the value "xs:integer" is not derived from "feet". Obviously, the value is matched by type "xs:integer". Hence, "xs:integer" is not a subtype of "feet", and the expression above is ill-typed. Is my reasoning correct? If so, does this signal an error in the static semantics or is there something inherently "wrong" with the expression above (justifying the ill-typedness)? --Stijn Vansummeren Limburgs Universitair Centrum Universitaire Campus Gebouw D 3590 Diepenbeek Belgium

Received on Thursday, 20 November 2003 11:45:57 UTC