Re: IfExpr has a mandatory else clause

Hello,

  I am really interested in the update, modify and delete aspect of XQuery.
Could someone
provide some pointers as to how existing products implement those features.

  My questions (which I am looking for some kind of references):

  (1) Assuming XQuery is built directly on top of native XML datatype,
instead of DBMS form of storage,
how do update, modify and delete of individual data fields impact the
performance of database?

  (2) Do any Xquery implementations offer features that allow one to
extract/remove an element in its serialized format?

  (3) Do any Xquery implementations allow one to splice together new XML
document from multiple other documents? Or the reverse of it, which allows
one to quickly take apart a big XMLdoc into multiple smaller ones?

  (4) Would features in 1~3 be useful now? What about in the future?

 Thanks,
Jimmy