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Re: Do we need the restrictions on the <base> element?

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Thu, 07 Jun 2007 17:39:19 -0500
Message-ID: <46688917.40000@mit.edu>
To: Laurens Holst <lholst@students.cs.uu.nl>
CC: "public-html@w3.org" <public-html@w3.org>

Laurens Holst wrote:
> XBL is again just one of the languages. If you’d include XBL directly 
> into HTML

The question is why you would do this.  The whole point of XBL is to have a 
shared binding definition living outside the HTML file, with all URI resolution 
in that binding happening relative to the _binding_.  Including the XBL inline 
more or less defeats the purpose, unless you're using it multiple times in that 
one page.

> Well, I think you mentioned tests of your own without giving any 
> specific numbers, where are those

True.  ;)  I'd need to rerun the tests to regenerate the numbers, which I'm not 
in a position to do in the next month or two due to time constraints.  But I'm 
happy to do that before a final resolution on this issue, again subject to time 
constraints.  Given your numbers I will in fact need to do that, if I can.

> Attached are 2 testcases. One for XHTML (which uses xml:base and 
> recursive lookup), and one for HTML.

Of course there are differences other than just xml:base handling between the two...

> Furthermore, deeper nesting does make it a little slower, but the 
> slowing is relatively insignificant

It's 7%.  That's usually significant enough to reject changes if they cause a 
regression of that magnitude, for what it's worth.

> and happens in both cases, so I wouldn’t credit this difference towards the baseURI implementation.

Indeed.

> These results make perfect sense because, is a couple of simple "if 
> (!@xml:base) return parent.baseURI;" iterations really going to make any 
> noticable difference?

Depending on how many other attributes the elements have and how many elements 
there are, absolutely.  Note that the 10-deep nesting is about an order of 
magnitude less than what happens on typical websites, by the way.  And there are 
usually more attributes flying around.

> Binary check, method call, return value, these are some of the simplest 
> operations possible.

Binary check in this case is not necessarily O(1) in number of attributes. 
Method call can be a very expensive proposition (virtual methods).

> If this would matter in any significant way, then 
> you’d better remove all those subroutines from all your code 

Inlining code is a common optimization technique, yes.  Usually done by the 
compiler.  ;)

> Sure, I guess it’s odd, but that’s what I’ve been talking about. UAs 
> already do it with <base> in HTML

Which is sad, but there it is.

> and Firefox with xml:base in XHTML as well.

Testcase?  That's not what I see over here.

-Boris
Received on Thursday, 7 June 2007 22:39:30 UTC

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