From: "Jeni Tennison" <>
> Nice chapter! On the "what to do about ambiguity" front, you mention
> adding an except pattern and using explicit disambiguation rules. A
> third option would be to use type systems that support you saying
> "this value is *both* X and Y".
>...
> You can think of this as multiple inheritance (a new, anonymous, type
> is inherited from both xs:boolean and xs:integer, and the <foo>
> element ends up either being a xs:boolean or an xs:integer, or this
> new anonymous type). A language that used such a type system would
> have to use the usual methods for disambiguation (such as those you
> list in your chapter) in situations where polymorphic operators or
> functions were used with such a type.
What a splendid idea! Too bad it hasn't infected XQuery/XPath 2.0.
Are you aware of any work underway on a query/transform model with a more
inclusive type system?
Bob Foster
