I changed it to this for now

   The "metalink:url" element contains the IRI of a file.  All IRIs
   contained in each metalink:resources element SHOULD lead to identical
   files.

looking a bit more, maybe this should be defined under <file>

   The "metalink:file" element represents an individual file, acting as
   a container for metadata and data associated with the file.

or <resources>,

   The "metalink:resources" element acts as a container for metadata and
   data associated with the listed files.  It contains one or more
   metalink:url child elements.  It can also contain one or more
   metalink:metadata child elements.

 because we want this to include <metadata> (anyone come up with a
better name? :), that is a torrent or metalink listed in <metadata>
won't be the same file as in <url> but will eventually lead to it if
you use that <metadata>



On Tue, Jun 30, 2009 at 4:59 PM, Anthony Bryan<[email protected]> wrote:
> On Thu, Jun 25, 2009 at 8:27 PM, Peter Poeml<[email protected]> wrote:
>> Hi!
>>
>> There is one thing in the Internet Draft that I'd like to bring to our
>> attention. Section 4.2.18 sets up a a strong requirement:
>>  All IRIs MUST lead to identical files.
>>
>> While surely this would be the intention, in practice I know more
>> examples where this either isn't the case, and albeit attempted it is
>> hard to assure.
>>
>> Content verification is there to help -- one of the purposes of metalinks.
>>
>> It might make sense to put this in a different way.
>>
>> Without any content verification being done (well, it is optional!), it
>> is a relatively hard requirement to make. When a content delivery
>> infrastructure reaches a certain scale, it becomes difficult though, as
>> we know. In particular this is true for collaborative mirror networks
>> formed by volunteers, where, in fact, the referenced IRIs might be
>> outside of the control of the content provider at all. (Security comes
>> into play here as well.)
>
> the current text is lacking, I'm glad you brought it up! at the least
> it should be something like:
>
> All IRIs under each "metalink:file" container Element SHOULD lead to
> identical files.
>
> because we don't want ALL the IRIs under separate <file> elements to
> lead to identical files.
>
> yes, MUST is too strong. the point is that the by design, IRIs that
> are included in a metalink SHOULD lead to identical files.
> will metalinks contain IRIs that aren't identical files? yes. do we
> want it to no longer be a valid metalink if a mirror network is out of
> sync & a file isn't identical? no
> I'm just trying to document the design purpose, that each IRI is a
> valid way to get the same exact file, under perfect conditions.
>
> clients should weed out files that have different sizes, & reject
> chunks that don't have the correct checksum, etc. a  metalink
> generators will attempt to include IRIs that point to identical files
> to be most helpful, but we want to protect against accidents or
> malicious people that would possibly want to lead to incorrect
> downloads.
>
> maybe content verification should be required for future versions (as
> in this version for the IETF)? even tho it is extremely important,
> some lazy implementers :) did not want to add support. as of now, I
> think only TheWorld browser does not support checksums. it's clear
> that most implementers see the value in it.
>
>> I would tend to make this a SHOULD, for practical reasons. Also, the
>> text could/should expand both on the implications.
>
> care to throw in some expansion text? :)
>
>> Alternatively, would the following be an idea?
>>  All referenced IRIs SHOULD lead to identical resources, if the
>>  Metalink includes a "metalink:verification" container with at least
>>  one "metalink:hash" element. All referenced IRIs MUST be identical, if
>>  the latter is not the case.
>
> If the Metalink Document includes a "metalink:verification" container
> element with at least one "metalink:hash" element, all referenced IRIs
> SHOULD lead to identical resources.
> If the Metalink Document does not include a "metalink:verification"
> container element with at least one "metalink:hash" element, all
> referenced IRIs MUST be identical.
>
> I don't know, do you think that is necessary or better?
>
> --
> (( Anthony Bryan ... Metalink [ http://www.metalinker.org ]
>  )) Easier, More Reliable, Self Healing Downloads
>



-- 
(( Anthony Bryan ... Metalink [ http://www.metalinker.org ]
  )) Easier, More Reliable, Self Healing Downloads

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