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[ontolog-forum] FW: URIs and Unique IDs [xfrd from [oor-forum]]

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Peter Yim" <peter.yim@xxxxxxxx>
Date: Fri, 7 Nov 2008 08:47:27 -0800
Message-id: <af8f58ac0811070847j11bee20wf1dd3209af8c5593@xxxxxxxxxxxxxx>
Mike Uschold was just talking about this subject matter (a week or so
ago) in his lightning talk called "A URI Crisis" at ISWC 2008 (at
Kar;sruhe, see:
).    (01)

Since the issue is definitely of concern and interest to the broader
Ontolog community, may I suggest we move the conversation to
[otnolog-forum] where Mike can also chime in ... since he started it
all. (I'll forward this thread over ... pick it up from there, if you
please.)    (02)

Regards.  =ppy
--    (03)

On Fri, Nov 7, 2008 at 7:57 AM, Evan Wallace <ewallace@xxxxxxxxxxxx> wrote:
> In the Semantic Web or when using semantic web languages, the primary
> names/identifiers for classes,
> properties and individuals (instances) are http URIs . This is
> fundamental to the languages and the way
> tools support the languages. RDF data and OWL ontologies are typically
> stored and accessed as web
> documents (and OWL imports is the typical mechanism used for
> modularizing this information). The
> RDF data model is triple based and the OWL model is axiom based. How one
> would make these languages
> and their tools work with the Object Oriented approach and services in
> the Handle System is far from obvious.
> Am I missing something? Is there a document describing how these things
> could be used together? Until
> I see a document describing how this would work, I don't see how the
> Handle System will help manage
> identifiers or any other information for semantic web resources.
> -Evan    (04)

>>  ----------
>> From: John F. Sowa <sowa@xxxxxxxxxxx>
>> Date: Thu, Nov 6, 2008 at 11:17 PM EST
>> Subject: Re: [oor-forum] FW: URIs and Unique IDs
>> To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>
>> Leo and Steve,
>> For naming schemes, there are only two options:
>>  1. Free for all naming scheme (e.g., people can name themselves
>>     and their children, pets, cities, etc., anything they please).
>>  2. Regimented naming scheme (some constraints imposed).
>> Option #1 usually results in multiple entities with the same
>> names.  Option #2 requires some kind of centralized registry
>> system that enforces whatever constraints are agreed.
>> The simplest kind of constraint is something like GENSYM in LISP.
>> Each time it is called, it generates a symbol that is guaranteed
>> to be distinct from every other symbol it has ever generated.
>> But for many kinds of things, such as people, computer programs,
>> and ontologies, we may need some kind of versioning mechanism.
>> We might want to talk about some specific version of Linux,
>> or we might want to refer to some person as a child or an adult.
>> Before we can even begin to talk about a registry for handling
>> versions, we have to agree on a lot of identity criteria.
>> When are two ontologies versions of one another?  How different
>> do two versions have to be before they are considered distinct?
>> Who decides?
>> John    (05)

>> ----------
>> From: John Graybeal <graybeal@xxxxxxxxx>
>> Date: Thu, Nov 6, 2008 at 7:45 PM PST
>> Subject: Re: [oor-forum] FW: URIs and Unique IDs
>> To: ray@xxxxxxxx, OpenOntologyRepository-discussion 
>> For what little it's worth, I've taken a moderately detailed look at
>> handles, and I reached the same conclusion some others have:
>> it moves the existing problems of URIs around to other parts of
>> the architecture, but doesn't fundamentally eliminate any of them,
>> and doesn't provide enough capability improvements or social
>> improvements to outweigh the social and adoption costs. (It may
>> be better than minted URIs -- it wasn't obviously better to me,
>> but I'm not an expert -- but I thought not sufficiently better to
>> abandon minted URIs.)
>> I'll be interested to hear others' reactions.  I think it may have been
>> discussed on the semantic-web list, so might be worth checking
>> the archives before posting.
>> John    (06)

> Steve Ray wrote Thu, Nov 6, 2008 at 7:30 PM EST:
>> For identifier resolution, it could work for a variety of things, so sure.    (07)

>> *From:* Obrst, Leo J. [mailto:lobrst@xxxxxxxxx]
>> *Sent:* Thursday, November 06, 2008 6:40 PM
>> *To:* ray@xxxxxxxx; OpenOntologyRepository-discussion
>> *Subject:* RE: [oor-forum] FW: URIs and Unique IDs
>> Steve,
>> Thanks. Do you think this would be useful for the Semantic Web
>> community too? I.e., should this be pushed to the semantic-web@xxxxxx
>> <mailto:semantic-web@xxxxxx> list?
>> Thanks,
>> Leo
>> _____________________________________________
>> Dr. Leo Obrst The MITRE Corporation, Information Semantics
>> lobrst@xxxxxxxxx Information Discovery & Understanding, Command and
>> Control Center
>> Voice: 703-983-6770 7515 Colshire Drive, M/S H305
>> Fax: 703-983-1379 McLean, VA 22102-7508, USA    (08)

>> *From:* oor-forum-bounces@xxxxxxxxxxxxxxxx
>> [mailto:oor-forum-bounces@xxxxxxxxxxxxxxxx] *On Behalf Of *Steve Ray
>> *Sent:* Wednesday, November 05, 2008 7:02 PM
>> *To:* 'OpenOntologyRepository-discussion'
>> *Subject:* Re: [oor-forum] FW: URIs and Unique IDs
>> I think we should be taking a hard look at Bob Kahn's ideas of the
>> Handle System. Take a look at http://www.doregistry.org. His idea of
>> handles bypasses URLs and DNS and provides a clean resolution system
>> at the object level, which would appear to work nicely with
>> ontologies, and pieces of ontologies. One would still have to ensure a
>> clean configuration management system ran on top of it all.
>> - Steve    (09)

---------- Forwarded message ----------
From: Obrst, Leo J. <lobrst@xxxxxxxxx>
Date: Fri, Oct 31, 2008 at 10:32 AM
Subject: [oor-forum] FW: URIs and Unique IDs
To: OpenOntologyRepository-discussion <oor-forum@xxxxxxxxxxxxxxxx>    (010)

I'm cross-posting this. Versioning is definitely an issue we need to
address for OOR, and though we may derive our methods from others, we
should certainly consider the ramifications now.    (011)

Leo    (012)

Dr. Leo Obrst       The MITRE Corporation, Information Semantics
lobrst@xxxxxxxxx    Information Discovery & Understanding, Command and
Control Center    (013)

Voice: 703-983-6770 7515 Colshire Drive, M/S H305
Fax: 703-983-1379   McLean, VA 22102-7508, USA    (014)

From: semantic-web-request@xxxxxx [mailto:semantic-web-request@xxxxxx]
On Behalf Of Michael F Uschold
Sent: Thursday, October 30, 2008 5:15 AM
To: semantic-web@xxxxxx
Cc: aldo.gangemi@xxxxxxxxx; Conor Shankey; Peter Mika; Ora Lassila;
Pan, Dr Jeff Z.; Tim Berners-Lee; Frank van Harmelen;
Subject: URIs and Unique IDs    (015)

I'm resending this message to the semantic web discussion group for the record.    (016)

On Wed, Oct 29, 2008 at 3:53 PM, Michael F Uschold <uschold@xxxxxxxxx> wrote:    (017)

Currently there is no accepted practice on how/whether to migrate to
new URIs when a new version of an ontology is published. This is
largely due to the fact that there is no good technology for managing
versioning, and the W3C consciously (and probably sensibly) decided
not to address the issue.  Versioning information is meant to be
placed on a version annotation.    (018)

However the current situation is like the wild West, and everyone will
be doing different things, resulting in a mess.    (019)

Wordnet published a new version and minted all new URIs even though
many or most of the entries were semantically identical.
The SKOS working group is currently considering the pros and cons of
various options. One is to adopt all new URIs in a new namespace, just
like Wordnet. Another is to keep the exact same name space, and change
the semantics of a small number of terms while keeping the same URI. A
third is to keep the same URI for the unchanged terms, and mint new
URIs for the terms with different semantics.    (020)

This is a problem because they have no guidelines, they are basically
stumbling along in the dark.    (021)

I believe that this is an urgent matter that needs attention to
prevent a nightmare from unfolding.    (022)

In the current state of semantic web use, it may not matter to much
what choice the SKOS team chooses. This is mainly relatively few
applications will be impacted, which may be due to the fact that the
applications are not driven by the ontologies.    (023)

However, when usage of ontologies and ontology-driven applications
becomes more mainstream, the differences could be profound. Given that
this issue is intimately tied up with versioning, and that we have no
good solutions yet, do we continue to throw our hands up and punt?
Absolutely not, it is essential that a good precedent is set ASAP that
is based on sound principles.    (024)

Here is how.    (025)

We should imagine a future where ontology versioning is handled
properly and do things that are going to make things easy to migrate
to that future. We don't know how the versioning black box will work,
but we should be able to make some clear and definitive statements
about WHAT it does.    (026)

For example, in the future, ontology-driven applications will be
fairly mainstream. URIs are used as unique identifiers. When
applications are driven from ontologies, then they will break if you
change the semantics in mid-stream.  Imagine an application that
relied on the semantics of broader as it was originally specified with
transitivity.  They loaded data that was created using that semantics.
Then the SKOS spec changes and broader is no longer transitive. New
datasets are created according to this new meaning. The application
loads more data. It needs to know which data is subject to transitive
closure and which is not. This is impossible, if the same SKOS URI is
used for versions with different semantics.  They are different
beasts, and thus MUST have different URIs.    (027)

Similarly, if SKOS mints a whole new namespace and changes all the
URIs, the application also has a problem. It has datasets with the old
URI and datasets with the new URIs. This means that the datasets will
not be linked like they should, they will treat the two different URIs
for the same thing as being different.  If one wanted to go into
OWL-Full, one can use owl:sameAs, but this is not very practical.  The
only reasonable solution is to have the same URI for things with the
same semantics.    (028)

Thus, any ontology versioning systemof the future will rely on these
two principles:
1. If the semantics of a term changes, then it needs to have a new unique ID.
2. If the semantics of a term does NOT change, then it should maintain
the same ID in any future versions.    (029)

If either of these two guidelines are broken, then so will the
ontology-driven applications of the future.    (030)

These maxims hold without exception for any standards that are
formally released as standards.
A question arises if we need to hold to the same standards for
standards like SKOS which was never formally blessed.    (031)

The practical difficulties will be the same whether the standard is
blessed or not. It only really depends on whether the standard is a de
facto standard,or whether it is getting significant use. If users
build things and ontology producers break things through carelessness,
this will hinder semantic web technology adoption.    (032)

Another question is what to do if the original standard is belived to
be incorrect, and the new one is the fixed one. Can one then keep the
same URI?
Again, the answer should be informed by the impact on applications.
The same problems will occur if you change the semantics and keep the
same URI even if you are fixing a mistake.  The URI with the wrong
semantics must keep its original unique ID.    (033)

Michael Uschold
---    (034)

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