RE: [xri] [Glossary] Definition of "Resource" and "Attribute"

[Drummond Reed <Drummond.Reed@onename.com>]

Mike,

Good point, use cases always help clarify terms. In fact here's a good one
from the IETF ResCap spec
(http://www.ietf.org/internet-drafts/draft-ietf-rescap-req-01.txt) that also
happens to include its own definition of attribute:

"An attribute is a named characteristic of a resource identifier with a
value that is meaningful in the context in which it is used.  An example of
an attribute might be a content type that an email address is capable of
receiving."

Note the phrase, "meaningful in the context in which it is used". That means
the attribute "content type that an email address is capable of receiving"
is an attribute of the resource "email address". 

So the use case is that a user agent such as a mail client wants to retreive
an attribute - the supported content types - of a resource - an email
address. While the abstract concept "supported content types" could be a
resource on its own, being able to resolve the abstract concept "supported
content types" as a resource doesn't do the user agent any good unless it
wants to know something about the schema of "supported content types" - such
as the enumerations of MIME types.

But in this case what the user agent needs is the supported content types of
a specific email address - joe@example.com. This specific set of supported
content types supported by joe@example.com can ONLY be identified in the
context of that specific resource. 

So maybe I should modify my proposed definition of "attribute" along the
lines of the one provided in ResCap:

	"An attribute is an identifiable characteristic of a resource whose
value is meaningful in the context of the resource it describes."

=Drummond   

 

-----Original Message-----
From: Lindelsee, Mike [mailto:mlindels@visa.com]
Sent: Thursday, February 27, 2003 4:48 PM
To: 'xri@lists.oasis-open.org'
Subject: FW: [xri] [Glossary] Definition of "Resource" and "Attribute"

Drummond,

I understand the distinction you are making with the definition of
attribute, but I don't necessarily see the need for it.  Perhaps you could
walk me through a couple of use cases that would make clear the need to
identify information exclusively in the context of a resource.  I would also
like you to then show me how that wouldn't be already covered by allowing
resources to "point" to other resources as "attributes."

Mike

> -----Original Message-----
> From: Drummond Reed [mailto:Drummond.Reed@onename.com]
> Sent: Thursday, February 27, 2003 3:59 PM
> To: 'xri@lists.oasis-open.org'
> Subject: RE: [xri] [Glossary] Definition of "Resource" and "Attribute"
> (lo ng)
>
>
> Mike (and Gabe before him): good stuff. The main reason I
> sent that opening
> salvo was to help folks realize how large an impact to the
> whole effort even
> small issues with these core terms have.
>
> The second reason is that, while it might seem like the term
> "attribute" may
> not be that important, in my experience with both XNS and
> Liberty, it ends
> out being very important - almost as important as "resource".
> Being able to
> unambiguously and persistently reference an attribute in the
> context of a
> specific resource is critical when it comes to security,
> digital identity,
> DRM, and many other applications of XRIs.
>
> That said, I agree with you, Gabe, and Bernard that we should
> just stick
> with the URI spec definition of resource as "anything that
> has identity" and
> not try to define it further. It's not worth splitting hairs
> over whether
> simple attributes actually have identity outside of the
> resource that they
> describe.
>
> I think your definition of attribute as " data, metadata or
> other resources
> associated with a resource" is pretty close to the mark but the words
> "associated with a resource" don't quite fully distinguish
> the two things I
> think are most important about attributes vs. resources:
>
> 1) Attributes are always relative, i.e., they only exist in
> the context of a
> specific resource, and
> 2) A special kind of attribute - an identifier - exists for
> the special
> purpose of forming an association with ANOTHER resource (that's our
> definition of identifier).
>
> To capture these two nuances, here's a modification to your proposed
> definition of "attribute":
>
>       Data, metadata or other resources that describe a
> specific resource.
> Attributes are always relative to the resource they describe.
> Identifiers
> are an attribute of one resource whose purpose is to form an
> association
> with another resource.
>
> How's that work?
>
> =Drummond
>
>