About

This page is for XRI TC members to collaborate on drafting a white paper on Abstract Identifier Architecture as part of our ongoing dicussions with the W3C TAG (see XriTcW3cTag). Initially this page will be used to draft and discuss proposed sections of this document. As the document evolves it is expected to migrate to an independent document maintained in the TC's document repository.

Definitions

The following definitions are proposed:

Abstract and Concrete Identifiers

In the context of a given communications protocol:

Descriptors

In the context of a given communications protocol:

Synonyms

In the context of a given communications protocol:

Illustration

Following is a conceptual diagram showing how a layer of abstract identifiers is constructed over a layer of concrete identifiers.

http://www.oasis-open.org/committees/download.php/29401/abstract-identifier-architecture-v1.jpg

Note that in order to resolve abstract identifiers of abstract resources into concrete identifiers that can be used to retrieve resource representations, a special class of concrete resources called resource descriptors is required. Resource descriptors also have their own concrete identifiers.

Terminology note: The terms resolve or discover are often applied to requesting a descriptor while the terms retrieve or access are often applied to requesting a representation.

Examples

The following tables provide examples of this architectural model.

DNS

Layer

Identifier

Example

Comment

Abstraction

Domain name

www.example.com

Delegates from right to left

Description

Nameserver Address + Domain Name + Record Type

206.194.13.5 + "www" + A

UDP ==> DNS Resource Record

Representation

IP Address

196.120.45.32

Access via TCP/IP

DOI (Handle System)

Layer

Identifier

Example

Comment

Abstraction

DOI

10.1000/182

Delegates from left to right

Description

DOI proxy URI

http://nascent.nature.com/openhandle/handle?id=10.1000/182&format=rdf&mimetype=application/xml

HTTP ==> DOI Resource Metadata Declaration

Representation

URI + others

http://www.doi.org/hb.html

Access via URI-identified protocol

XRI

Layer

Identifier

Example

Comment

Abstraction

XRI

=drummond

Delegates from left to right

Description

XRI proxy URI

http://xri.net/=drummond?_xrd_r=application/xrds+xml

HTTP ==> XRDS

Representation

URI + others

http://www.equalsdrummond.name

Access via URI-identified protocol

Conclusions

This is only a placeholder – additional conclusions will be added as work on the paper progresses.

In the context of the same communications protocol, the same identifier cannot serve as both an abstract and concrete identifier. To support abstract identification and metadata discovery in addition to representation retrieval requires either:

  1. Using the same identifier in the context of two different protocols – a metadata resolution protocol and a representation retrieval protocol.
  2. Using the same protocol with two different identifiers, and creating a mapping between the abstract and concrete identifiers.

AbstractIdentifierArchitecture (last edited 2009-08-12 18:07:23 by localhost)