[xquery-talk] RE: Future of XQuery and XQuery Update Faclilty
lord at emf.net
Mon Oct 22 14:20:48 PDT 2007
Jonathan Robie wrote:
> Perhaps another way of putting it: what is central here is the updates
> that are to be done. To specify the updates to be done, an application
> would write queries that contain updates, it would not generate a
> pending update list in XML so that a different application can do the
> updates. Distributing a single update among multiple applications is
> not a simplification.
Ugh. This is the problem of people not wanting to write in
"environment passing style". There's a trivial transform from queries
that contain XQUF-style updates to a program in "straight XML" style but
it involves threading through an extra parameter to every function and
making heavy use of tail calls. But, those awkwardnesses are, at most,
just a question of syntax -- no need for "declare updating function".
> The pending update list is a way of defining the semantics of the
> language. We don't expose the formal semantics as XML either, nor the
> import mechanism, nor many other aspects of our semantics. Most users
> will use one XQuery engine for a given update, and simply issue an
> update and observe the results.
Updates aren't the *only* kind of extension that need some concept of
environment passing style. It's an open-ended design pattern. Any
update-specific solution is suspect on programming language theory grounds.
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