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RE: Versioning goals doc

From: Larry Masinter <masinter@parc.xerox.com>
Date: Wed, 30 Sep 1998 07:32:34 PDT
To: "Babich, Alan" <ABabich@filenet.com>, "WebDAV WG" <w3c-dist-auth@w3.org>
Message-ID: <000901bdec7f$2a1bab20$15d0000d@copper-208.parc.xerox.com>
> Definitions:
> "5. A variant is a representation of a resource. A resource
> may have one or more representations associated with it at
> any given time. Not all versioning DAV servers need support
> variants."
> This definition needs work. My understanding of variants is 
> that variants are not merely mechanically generated alternate
> renditions of the same document that all share the 
> properties of the original rendition of the document. My
> understanding of variants is that they are full status
> resources, and that they have their own properties.

In HTTP, a variant may or may not be a separate resource. However,
for the purpose of WebDAV, I would propose that any variant than
can be authored independently must be a separate resource.

> Furthermore, variants may exist even if versioning doesn't.
> Variants are independent of versioning.
> The principal use case for variants seems to be
> language translations of documents. 

There are a variety of cases for variants. The most common case
for variants in use in the web today seems to be to have different
variants of the page depending on which version of browser your
User-Agent string reports. Other variants may depend on other
factors. Content may 'vary' on any of a variety of request headers.

> Obviously, a
> translated version of a document has its title property
> translated as well as its content, etc.

This isn't 'obvious' at all. 

> In other words, variants are separate documents (resources), 
> and they have nothing directly to do with versioning.

The design of versioning needs to account for the relationship
of versions of a resource and versions of its variants for
all of the cases of uses of variants. Since there are several
cases, a case analysis is necessary. You've analyzed only
one of the cases.

> The original English document and a German variant of
> it may both be versioned. It is possible that each
> revision of the English document has a variant that is
> a revision of the German variant. However, it is also
> possible that the translator guy was busy, and so
> didn't translate some of the revisions. So some
> of the revisions don't have corresponding variants
> in the German document.
> Here is my suggested rewording:
> "5. One resource is said to be a variant of another
> resource when a sufficiently strong relationship exists 
> between the content of the two resources, e.g., when each
> resource is a language translation of the other.
> In this regard, "resource" is, of course, understood to 
> include the case of a resource that is a revision
> of an abstract versioned resource."

This is one use of 'variant' but not comprehensive.

> Then, of course, we need goals for variants.
> Otherwise, why have them at all?

Variants are defined in HTTP/1.1. Variants are used by web servers.
WebDAV's goal is to support distributed authoring and versioning for the
Web. Thus, WebDAV needs to define distributed authoring and versioning
for variants, since they are used in the web.

> "13. Given a resource, it must be possible to retrieve
> all the resources that are considered to be variants of it.

This is unworkable in the case of computed variants.

> 14. Server support for variants is optional."

Having this in the 'goals' document will just give you trouble,
since it can be interpreted in so many ways.

> Alan Babich
Received on Wednesday, 30 September 1998 10:32:55 UTC

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