[xquery-talk] RE: Future of XQuery and XQuery Update Faclilty

[Jonathan Robie]

Thomas Lord wrote:
> Why is there a need for XQUF?

Because people need to make changes to data.

> Pending updates could be expressed in straight XML.   Why
> is a new and non-externalizable type needed to supplement
> XDM?   

The pending update list is purely an abstraction used internally by an 
implementation. What benefit would there be to externalizing it in a 
standard way? How would you propose to do this with "straight XML"?

> It seems a horrible rule, not least because of the
> segregation of "declare updating function" procedures from
> "declare function" in the static type rules for XQuery.

A great deal of optimization in XQuery is based on the assumption that 
there are no side effects. Updates invalidate that assumption. Also, the 
user generally knows that calling a function does not result in changes 
to the underlying data. For both the compiler and the user, I think it's 
helpful to identify functions that update.

Jonathan