Re: Second Last Call: <draft-hammer-hostmeta-16.txt> (Web Host Metadata) to Proposed Standard -- feedback

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Mark, I will work with the authors on proposed wording to describe the
context in which this technology is most applicable, and post again once
we've done that.

On 7/13/11 5:35 AM, Mark Nottingham wrote:
> Personally, I think Informational is most appropriate (and probably easier), but a paragraph or two of context, as well as corresponding adjustments, would work as well. 
> 
> Cheers,
> 
> 
> On 13/07/2011, at 5:36 AM, Peter Saint-Andre wrote:
> 
>> On 6/21/11 11:08 PM, Mark Nottingham wrote:
>>> Generally, it's hard for me to be enthusiastic about this proposal,
>>> for a few reasons. That doesn't mean it shouldn't be published, but I
>>> do question the need for it to be Standards Track as a general
>>> mechanism.
>>
>> How about publishing it on the standards track but not as a general
>> mechanism (i.e., why not clarify when it is and is not appropriate)?
>>
>> Clearly, both service providers (Google, Yahoo, etc.) and spec authors
>> (draft-hardjono-oauth-dynreg-00, draft-hardjono-oauth-umacore-00) have
>> found hostmeta somewhat useful in certain contexts.
>>
>> RFC 2026 says:
>>
>>   A Proposed Standard specification is generally stable, has resolved
>>   known design choices, is believed to be well-understood, has received
>>   significant community review, and appears to enjoy enough community
>>   interest to be considered valuable.
>>
>> and:
>>
>>   Usually, neither implementation nor operational experience is
>>   required for the designation of a specification as a Proposed
>>   Standard.  However, such experience is highly desirable, and will
>>   usually represent a strong argument in favor of a Proposed Standard
>>   designation.
>>
>> The spec seems to be stable at this point, it's received significant
>> review, people seem to understand what it does and how it works, it's
>> had both implementation and operational experience, and it appears to
>> enjoy enough community interest to be considered valuable in certain
>> contexts. I also think it has resolved the design choices and solved the
>> requirements that it set out to solve, although you might be right that
>> it doesn't solve all of the problems that a more generic metadata
>> framework would need to solve.
>>
>> As a result, it seems like a fine candidate for Proposed Standard, i.e.,
>> an entry-level document on the standards track that might be modified or
>> even retracted based on further experience.
>>
>>> Mostly, it's because I hasn't really seen much discussion of it as a
>>> general component of the Web / Internet architecture; AFAICT all of
>>> the interest in it and discussion of it has happened in more
>>> specialised / vertical places. 
>>
>> Again, perhaps we need to clarify that it is not necessarily a general
>> component of the web architecture, although it can be used to solve more
>> specific problems.
>>
>>> The issues below are my concerns;
>>> they're not insurmountable, but I would have expected to see some
>>> discussion of them to date on lists like this one and/or the TAG list
>>> for something that's to be an Internet Standard.
>>>
>>>
>>> * XRD -- XRD is an OASIS spec that's used by OpenID and OAuth. Maybe
>>> I'm just scarred by WS-*, but it seems very over-engineered for what
>>> it does. I understand that the communities had reasons for using it
>>> to leverage an existing user base for their specific user cases, but
>>> I don't see any reason to generalise such a beast into a generic
>>> mechanism.
>>
>> As discussed in responses to your message, XRD seems to have been an
>> appropriate tool for the job in this case. Whether XRD, too, is really a
>> general component of the web architecture is another question.
>>
>>> * Precedence -- In my experience one of the most difficult parts of a
>>> metadata framework like this is specifying the combination of
>>> metadata from multiple sources in a way that's usable, complete and
>>> clear. Hostmeta only briefly mentions precedence rules in the
>>> introduction.
>>
>> That could be something to work on if and when folks try to advance this
>> technology to the next maturity level (currently Draft Standard).
>>
>>> * Scope of hosts -- The document doesn't crisply define what a "host"
>>> is.
>>
>> This seems at least somewhat well-defined:
>>
>>   a "host" is not a single resource but the entity
>>   controlling the collection of resources identified by Uniform
>>   Resource Identifiers (URI) with a common URI host [RFC3986].
>>
>> That is, it references Section 3.2.2 of RFC 3986, which defines "host"
>> with some precision (albeit perhaps not "crisply").
>>
>>> * Context of metadata -- I've become convinced that the most
>>> successful uses of .well-known URIs are those that have commonality
>>> of use; i.e., it makes sense to define a .well-known URI when most of
>>> the data returned is applicable to a particular use case or set of
>>> use cases. This is why robots.txt works well, as do most other
>>> currently-deployed examples of well-known URIs.
>>>
>>> Defining a bucket for potentially random, unassociated metadata in a
>>> single URI is, IMO, asking for trouble; if it is successful, it could
>>> cause administrative issues on the server (as potentially many
>>> parties will need control of a single file, for different uses --
>>> tricky when ordering is important for precedence), and if the file
>>> gets big, it will cause performance issues for some use cases.
>>
>> It would be helpful to hear from folks who have deployed hostmeta to
>> hear if they have run into any operational issues of the kind you
>> describe here.
>>
>>> * Chattiness -- the basic model for resource-specfic metadata in
>>> hostmeta requires at least two requests; one to get the hostmeta
>>> document, and one to get the resource-specific metadata after
>>> interpolating the URI of interest into a template.
>>>
>>> For some use cases, this might be appropriate; however, for many
>>> others (most that I have encountered), it's far too chatty. Many use
>>> cases find the latency of one extra request unacceptable, much less
>>> two. Many use cases require fetching metadata for a number of
>>> distinct resources; in this model, that adds a request per resource.
>>>
>>> I'd expect a general solution in this space to allow describing a
>>> "map" of a Web site and applying metadata to it in arbitrary ways, so
>>> that a client could fetch the document once and determine the
>>> metadata for any given resource by examining it.
>>
>> That sounds like good input to a more generic approach. Many discovery
>> protocols do seem to have an inherent chattiness about them, but you
>> might be right that ideally the round trips could be kept to a minimum.
>>
>>> If hostmeta is designed for specific use cases and meets them well,
>>> that's great, but it shouldn't be sold as a general mechanism. So,
>>> I'm -1 on this going forward as a standards-track general mechanism.
>>> I wouldn't mind if it were Informational, or if it were
>>> Standards-Track but with a defined use case.
>>
>> Again, I think some clarifying language about the applicability of the
>> technology is in order.
>>
>>> Apologies for giving this feedback so late in the process; I knew
>>> hostmeta was there, just didn't have time to step back and think
>>> about it.
>>
>> And my apologies for taking so long to reply.
>>
>> Peter
>>
>> -- 
>> Peter Saint-Andre
>> https://stpeter.im/
>>
>>
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