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Re: HEAD (was Re: Link Verification)

From: <hallam@vesuvius.ai.mit.edu>
Date: Thu, 09 May 96 12:32:57 -0400
Message-Id: <9605091632.AA01806@vesuvius.ai.mit.edu>
To: Jeffrey Mogul <mogul@pa.dec.com>, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Cc: hallam@vesuvius.ai.mit.edu

>In other words, I think the correct action for your server to take
>for a HEAD request is to generate whatever it would generate for
>a GET request, but then just drop the entity-body on the floor.

I think that there is a large range of active content for which this
model fails. If the server is never going to generate the same entity
twice then it is pointless telling the client the content length, 
digest or any other parameter of the content which would not be the
same for a subsequent HEAD.

Does the spec specifically require a HEAD method to return content 
length? If not simply returning the entity content type would appear
to be sufficient.


Leaving asside the statement in the HTTP/1.0 spec the strict condition
of idempotence which Tim originaly stated has never been absolute.
For example in my email server I updated the "read" condition of a message
when it was accessed via a GET method but not when it is accessed by a
HEAD. This is well within the spirit of the "safe GET" but it isn't
idempotent.

I think it better to consider the HEAD method as strictly a means of 
retrieving whatever meta information concerning an entity may be
avaliable.


	Phill
Received on Thursday, 9 May 1996 09:52:18 EDT

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