[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Re: null call of document function

Subject: Re: null call of document function
From: Steve <subsume@xxxxxxxxx>
Date: Sat, 7 Apr 2007 20:46:40 -0400
Re:  null call of document function
Maybe you could give me some additional guidance? My situation is this:

I have a sql table 'alerts' which contains system messages to be
delivered to the user.

A call to my xsl template "getAlerts" calls a script which serves
these alerts up as XML and then clears them from the table.

In some cases I want a file my user is viewing to generate an alert.
My idea was to use the document function to insert the alert, and then
later in the script it would be available for the getAlerts template.

Are you suggesting it would be wiser to insert this Alert in my
processing script pre-transform? Some other suggestion?

-Steve

On 4/7/07, Michael Kay <mike@xxxxxxxxxxxx> wrote:
> What if I want to make a call to the document() function but
> I don't expect any value?

That presumably means you expect the call to have side-effects.

A call on the document function is analagous to an HTTP GET request, and
it's considered bad form for GET requests to have side effects:

http://www.w3.org/2001/tag/doc/whenToUseGet.html

At the XSLT level, calling document() and expecting side-effects has all the
problems associated with extensions functions that have side effects,
notably that the call is liable to be optimized away if the result isn't
used. In fact it's worse than extension functions, because:

(a) with extension functions, the optimizer might if you're lucky take into
account the possibility that the call has side-effects; with the document()
function this is unlikely

(b) the semantics of the document() function essentially say that if you
make the same call twice with the same URI, it only gets executed once.

In short - don't do it.

Michael Kay
http://www.saxonica.com/

Current Thread

PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
Email
First Name
Last Name
Company
Subscribe in XML format
RSS 2.0
Atom 0.3
Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.