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Re: Feedback on the ping="" attribute (ISSUE-1)

From: Henri Sivonen <hsivonen@iki.fi>
Date: Sat, 3 Nov 2007 10:42:29 +0200
Message-Id: <938A7FCC-1734-4811-9586-9369D48D6D98@iki.fi>
Cc: Ian Hickson <ian@hixie.ch>, HTML WG List <public-html@w3.org>
To: Julian Reschke <julian.reschke@gmx.de>

On Nov 3, 2007, at 01:10, Julian Reschke wrote:

[Hixie already reiterated that this is about idempotence--not  
"safety", so I'm not replying to the safety points.]

>> On Sun, 28 Oct 2007, Henri Sivonen wrote:
>>> That might work and could be a tad safer. It isn't in any way  
>>> theoretically pure from the RFC 2616 point of view, though, to  
>>> make HEAD and GET have different semantics beyond the response  
>>> body presence.
>> Indeed.
> Yes, and nobody suggested that.

It should be obvious that if browsers consistently used HEAD for  
pings, servers would have a *very* strong incentive to give HEAD and  
GET different semantics beyond the presence of the response body.  
Thus, the net effect of browsers using HEAD for pings would lead to a  
semantical divergence of HEAD and GET even if it weren't explicitly  
suggested or were explicitly suggested against.

Consider this from the point of view of an ad server. If user- 
operated browsers are known to use HEAD, you can be pretty sure that  
a GET is not an effect of a user following a link in a ping-aware  
browser. Thus, all GETs are noise. Ad servers care more about quality  
impression data than about RFC 2616, so it would make perfect sense  
to ignore GETs but not HEADs.

The larger effect of this would be that the trustworthiness of HEAD  
as a reliable way of obtaining metadata about GETtable resources  
would be diluted.

Henri Sivonen
Received on Saturday, 3 November 2007 08:42:52 UTC

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