Subject: Re: [Fwd: Article-level Document URIs]

From: "Paskin, Norman (DOI-ELS)" <[email-masked]>
Date: Mon, 11 Sep 2000 15:12:02 +0100

This posting was copied to me as it mentions DOIs.   (1) the ability to link
is surely the basis of the web, so is needed; (2) creating a system of
identifiers which Rob characterises as "open" to do it is possible - but
that's not really the point.

I am not commenting on the details of Rob's specific proposal here, but
making some general points.

The terms open and closed unfortunately carry overtones especially on the
web  which may be misleading; specifically, open = good, closed =
proprietary = evil, etc.  That's not I believe an accurate characterisation
in this case and I suggest using clearer terminology.  Open as used by Rob
appears to mean that given the item, one can construct the identifier by
inspection of the item or a detailed bibliographic record, and algorithm, a
property more correctly known as affordance, or derived identifiers.  Closed
appears to mean that the identifier is assigned by an agreed authority, like
country codes, etc (maybe we could call these assigned identifiers).   Both
have their uses.

Consider the most widely used and commercially useful non-Web identifiers:
UPC/EAN Bar codes for billions of objects; ISBNs for millions of books.
Both systems are what Rob calls closed (and I think more usefully described
as assigned in a controlled namespace).  It's not useful to assign your own
bar code to your pack of milk if you expect your grocery store to understand
it, though you could, or your own ISBN to a book if it already has one:
basically, the UCC/EAN namespace is more useful than your own namespace for
milk, the ISBN more useful for ordering from Amazon, etc.  What's important
is not how the number is arrived at, but its namespace and thereby wide
acceptability, authority etc.

Numbering does not require an agency and could clearly be automated and
distributed.  The namespace could be one which is assembled from derived
identifiers, as long as everyone follows the appropriate algorithm.  But
numbering is the least difficult of the issues: in particular an assigning
agency can help in controlling associated metadata (defining what this
number is identifying) as an aid to interoperability.  It may be argued that
we can/will be able to automate metadata control and collection too,  and do
this in a distributed fashion for web objects.  In my view, this is not yet
possible in a way which results in interoperability.   There are some
bibliographic identifiers with affordance ("open") - e.g. SICI.  As a
generalisation they are harder systems to maintain than dumb numbers and
they don't have associated metadata other than in the algorthmic
computation.  The CrossRef article linking system uses DOIs; some publishers
are using SICIs as part of the DOI, others are using other identifiers.
DOis therefore can contain either assigned or derived identifiers.

On the specific issues of linking between articles, some form of identifier
is clearly useful.   In the past, we've used open identifiers and algorithms
for human consumption; we call them bibliographic citations and they are
useful but not always unambiguous.  An automated identifier scheme must be
capable of dealing with linkage not just to articles but to the many new
forms of scholarly invocation- and ultimately to anything you choose to use
as a citation .  I've written more extensively on this under the heading of
E-Citations.   The issue of whether linkage can be best done by assigned
identifier mechanisms or on-the-fly algorithms (essentially derivable
identifiers) has been discussed in three NISO/DLF meetings on identifier
linkage (see links at www.niso.org).

I do not believe this question can be fully considered as one of a number
(identifier) in isolation.  The context is vital: the associated namespaces,
associated structured metadata, whether or not the identifier carries
intelligence, and having multiple identifiers for the same entity.  All this
has been cogently summarised in the indecs project, a small part of which is
reproduced below.

<<2.1   The principle of Unique Identification
Every entity should be uniquely identified within an identified namespace.
It is difficult to overstate the importance of this simple and commonplace
principle. At one level it can be said that the basis of interoperable
metadata is simply about the relationships of recognisably unique
identifiers. In pre-digital bibliographic and commerce systems, much of
their effectiveness depends on the robustness of identification systems: the
UPC/EAN product numbers, the ISBN book identifier and the CAE
composer/author/publisher identifier are among the most successful
identification systems in use in the world of content management, and form
the backbone of highly effective distribution systems in their respective
industries.
In contrast, where unique identifiers for major entities do not exist or are
poorly  implemented within a domain, data management costs are higher and
simple and effective systems difficult to develop. The absence of unique
"party" identifiers for creators and publishers among the major content
industries, the scarcely visible implementation of the ISRC for sound
recordings, and the lack of a standard agreement or licence identifier in
any copyright community are examples of gaps which are crippling for
interoperability within a domain, let alone between traditional domains.
Multi-media, multi-lingual, multi-national, multipurpose metadata also
requires that unique identification applies at all levels, including the use
of "controlled vocabularies" for values of properties such as measures, form
and type. In truly well-formed metadata the only "free text" properties of
an entity are found in its names or titles; an in some cases (for example,
in trademarks and in Actors Equity) even names may be protected to ensure
their uniqueness in a given domain.
Some issues which were once central to debates on identifiers have become
much less important in the electronic domain: in particular the question of
intelligence, and of multiple identifiers for the same entity.
Intelligent identifiers (that is, identifiers which carry some information
in their structure relating to the entity they identify, such as a format,
date or producer code) are of some value in particular circumstances, but
problems of ambiguity or volatility have rendered much of this intelligence
unreliable.
It is also less important that an entity may have more than one unique
identifier, even in the same domain. On the contrary, as entities like
multimedia become more complex, or parties such as publishers operate in
multi-media, multinational environments, it becomes inevitable that they
will acquire more and more domain identifiers, which may or may not require
reconciliation. The question of whether or how different identifiers for the
same entity should be reconciled is both practical and political and beyond
the scope of this document.
The development of domains or namespaces within the Internet has helped in
the relaxation of pressure on the need for absolute uniqueness in the
structure an identifier. URLs or URIs provide mechanisms for universal
disambiguation which allow even common terms to assume unique global status.
For wider interoperability the most important properties of an identifier
are (1) uniqueness within a domain; (2) stability (identifiers should never
be changed or transferred); (3) security, whether through protection by
watermarking or encryption, and/or by internal consistency through the use
of check digit algorithms; and (4) the availability somewhere of some basic
descriptive metadata for the entity identified, without which the identifier
has only limited use.>>

from:  http://www.indecs.org/results/archive.htm  the final version (pdf)of
the indecs "Metadata Framework: Principles, Model and Data Dictionary."
-------- Original Message --------
Subject: Article-level Document URIs
Date: Fri, 8 Sep 2000 09:23:43 -0700
From: Rob Cameron <[email-masked]>
Reply-To: Rob Cameron <[email-masked]>
To: [email-masked]

I have some questions for members of this list.   (1)  How important, as
a potential application of URIs/URNs, is the ability to link to
any article published in a journal, conference proceeding or
institutional report series?

If you think that this an important application, then (2) how important
is it that an article-linking solution based on open identifiers
be available?   By open identifiers, I am referring to identifiers
that can easily be worked out by scholars and librarians for the
great bulk of the published literature.  I contrast this with a
closed identifier model such as the DOI, in which documents have
identifiers only when rightsholders register those identifiers.

I ask these questions because I have been working in this area
and I have a strong interest in developing a system of unambiguous,
persistent identifiers for published contributions to our
collective knowledge archive, together with a library-based network
for resolving references.

We do have a specific proposal together with an implemented
prototype that comprehensively addresses this topic.   This has
recently put out as an Internet Draft; an HTML version of the
draft has working links to demonstrate the technology.

Before saying more about our proposal, I would like to ask (3) if
are you aware of any other URN-based proposals that address this
topic.  I acknowledge that RFC 2288 does note the syntactic issues
in addressing this problem using SICI document identifiers, but
there is no proposed system that builds on it.  Otherwise
I can't find any semblance of a proposal that would provide
a comprehensive URN-based solution based on an open
identifier model.

Turning to our proposal, we have focussed on the specific problem
of bibliographic linking, much narrower than we understand the
scope of the general URN work to be.   For one, this gives us
an extremely simple resolution model that emphasizes local library
services with respect to referenced documents.   Specifically,
a user in some-domain.edu will be first directed to
bibhost.some-domain.edu
for information and access to the cited item.  If the bibhost
does not exist, service is directed to a publisher-specified server
or to a global server.  The resolution hierarchy has been
implemented in a short bit of JavaScript that can be easily pasted
into HTML documents that use our framework.  (No browser modification
required.)

The emphasis on local library services allows libraries to provide
local context on access to items.  This includes access to paper-based
as well as digitally held items.  It includes access to site-licensed
materials that are otherwise not freely available.  It includes
other kinds of local context, such as document delivery options,
access to nonlocal items from partner libraries and the ability
to present items in the local language.   This is consistent with
the philosophy expressed in the SFX work, metadata-based approach
to article linking.

The focus on bibliographic reference also allows a relatively
simple solution to the namespace problem, at least to get started.
Our namespace has only three top-level domains: ISSN, ISBN and
RDNS.   However, RDNS is a parameterized domain that creates
individual namespaces for institutions that have a well-established
DNS name both owned by the institution and associated with it.
RDNS(sfu.ca) is the namespace for Simon Fraser University,
RDNS(bn.pt) is the namespace for the National Library of Portugal
and so on.

We think that our approach is philosophically consistent with the
URN concept as it applies to bibliographic linking.   However,
our mechanisms are different.   We have thus proposed that
it be created with its own URI scheme, "bibp" for bibliographic
protocol.   Significantly, this allows us to go beyond N2R or
N2L style resolution.  Although our Level 1 work deals only
with resolution, we think there is substantial area for
additional protocol development with respect to metadata sharing
(server-to-server interactions under BibP level 2).

We invite your comments on the Internet Draft entitled
Bibliographic Protocol Level 1: Link Resolution and Metapage Retrieval
http://search.ietf.org/internet-drafts/draft-cameron-tatu-bibp-00.txt
An HTML version with working BibP links (most recent browsers)
is available at
http://www.cs.sfu.ca/~cameron/draft-cameron-tatu-bibp-00.html

We also invite your answers to the three questions identified
above as a survey.

Robert D. Cameron, Ph. D.
Professor of Computing Science
Associate Dean of Applied Sciences
8888 University Drive
Simon Fraser University
Burnaby, B.C., Canada  V5A 1S6
http://www.cs.sfu.ca/~cameron/