[edits in 1.505] reworking errors SPARQL Query

I've changed 11.2.3.9 sop:datatype
  Returns a valid [RFC3066] language tag representing the XML schema
  language datatype for a variable.
to
  Returns the datatype of its argument if that argument is a typed
  literal. Otherwise it produces a type error.

and 11.2.3.8 sop:lang
  Returns a valid [RFC3066] language tag representing the XML schema
  language datatype for a variable.
to
  Returns an [RFC3066] language tag representing the XML schema
  language datatype of its argument if that argument has a language
  tag. Otherwise it produces a type error.

I used the lang change in langMatches:
  RFC3066 section 2.5 defines the language range '*' to match any
  tag. In SPARQL, the idiom langMatches( lang( ?v ), "*" ) will not
  match literals without a language tag as lang( ?v ) will produce a
  type error.


So basically, the argument for DATATYPE must be a typed literal, and
the argument to LANG must be a langed literal.




There is still more work to do on errors. For instance, Andy asked
what 1/0 is. XPath F&O has a large number of them[ERR], which we
implicitly use by defining our operators in terms of XPath functions.

For instance, the Operator Mapping Table[OPS] ties '/' to
op:numeric-divide[DIV]. (This is inspired by XQuery's similar
construct somewhere near [QOP].)

I think what's needed is some words about "errors" and "type errors"
and "other errors" derived from F&O.

[ERR] http://www.w3.org/TR/2005/WD-xpath-functions-20050915/#d1e10985
[DIV] http://www.w3.org/TR/2005/WD-xpath-functions-20050915/#func-numeric-divide
[OPS] http://unagi/2001/sw/DataAccess/rq23/#OperatorMapping
[QOP] http://www.w3.org/TR/xquery/#dt-gregorian
-- 
-eric

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