- From: Drummond Reed <drummond.reed@cordance.net>
- Date: Mon, 22 Sep 2008 00:03:11 -0700
- To: "'Dan Connolly'" <connolly@w3.org>, "'www-tag'" <www-tag@w3.org>
> -----Original Message----- > From: www-tag-request@w3.org [mailto:www-tag-request@w3.org] On Behalf Of > Dan Connolly > Sent: Thursday, September 18, 2008 9:47 AM > To: www-tag > Subject: a protocol analog to abstract/concrete identifiers > > > This abstract/concrete notion... > > [[ > * An abstract identifier is an identifier (arc) of a target > resource (node) that MUST NOT resolve directly to a > representation of that resource, but MAY resolve to a > description of that resource (descriptor). > > * A concrete identifier is an identifier of a target resource that > MAY resolve directly to a representation of that resource, but > MUST NOT resolve to a descriptor of that resource. > ]] > -- http://wiki.oasis-open.org/xri/AbstractIdentifierArchitecture > > ... has an analog at the protocol level. > > Given I1 which identifies X1, > when I do an HTTP GET on I1, > - if I get a 200 response, the body is a representation of X1 > - if I get a 3xx or 4xx response, any body I find is closer > to a "description" of X1. > > cf the spec for 300 Multiple Choices : > > "the response SHOULD include an entity containing a list of resource > characteristics and location(s) from which the user or user agent can > choose the one most appropriate." > -- http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.1 > > I suspect this analog is enough to meet whatever requirements > motivate the definitions of abstract/concrete identifiers. Dan, I agree that's a good analogy. It lines up well with the incisive analysis Eran Hammer-Lahav posted last week of the various options for using HTTP as a metadata discovery protocol [1]. >From an efficiency standpoint, the key challenge is what Eran calls "Direct Metadata Access": "Direct Metadata Access - enable direct retrieval of metadata without interaction with the resource itself. Before a resource is accessed, the consumer should have a way to fetch the resource's metadata without accessing the resource. This is important for two reasons. First, accessing an unknown resource may have undesirable consequences. After all, the information contained in the metadata is supposed to inform the consumer how to interact with the resource. The second is efficiency - removing the need to interact with the resource in order to get its metadata (which can reduce HTTP round-trips, network bandwidth, application latency, and overall waste)." What we're looking for is a solution that provides direct metadata access without violating the principles of Web architecture. =Drummond [1] http://www.hueniverse.com/hueniverse/2008/09/discovery-and-h.html
Received on Monday, 22 September 2008 07:04:54 UTC