RE: Referencing FOAF

Makx, Dan, et al.

My two cents because I see this issue cropping up repeatedly while linking 
data in new domains and geographies.

Linking data to vocabularies is in itself a big effort with existing 
tools. So, people rarely make the difference between predicate or value 
vocabularies. In fact, people link to what they consider as the best fit 
at that time and from trustable sources.
So, a mechanism to register/ version vocabularies will go a long way in 
promoting reuse. It is consistent with another area where the community 
has experience -  the approach of registering services (for reusing web 
services).
If newer versions of vocabularies come in future, it is the choice of the 
vocab developers to support backward compatibility or the consumers to 
move to the newer version (with any support the platform provides for 
discovering new versions).
It is expected that if there are choices of existing vocabularies that are 
well maintained (choice [2] in Makx note) or of unknown origin (choice 
[1]), unconstrained, rational consumers will first choose [2], and only if 
that does not work out, choose [1] or create their own. One would choose 
[3] for purely tactical reasons.
 
Regards,
--Biplav
 
 



From:
"Makx Dekkers" <mail@makxdekkers.com>
To:
"'Gillman, Daniel - BLS'" <Gillman.Daniel@bls.gov>, "'Public GLD WG'" 
<public-gld-wg@w3.org>
Cc:
"'Sandro Hawke'" <sandro@w3.org>, "'Phil Archer'" <phil@philarcher.org>
Date:
12/19/2012 02:00 AM
Subject:
RE: Referencing FOAF



Thanks, Dan.
 
You make very valid points, but I think those relate mostly to what I 
would call “value vocabularies”, things you use in the Object position in 
a triple, for example sets of concepts like the Library of Congress 
Subject Headings, EuroVoc terms, Geonames etc.
 
My message was more narrowly focused on predicate vocabularies, like DCMI 
terms, FOAF, DCAT, ADMS and was triggered by the discussion in the call on 
6 December on whether a W3C specification could rely on an external 
predicate vocabulary like FOAF that is not managed according to W3C rules 
and procedures.
 
But for value vocabularies, I agree that there is no sensible way to 
define “good” in the sense of “fit for purpose”. However, there could 
still be scope for defining “good” in terms of “well-defined and 
well-maintained” but maybe that’s not a subject that is in scope for this 
group.
 
Makx.
 
 
 
From: Gillman, Daniel - BLS [mailto:Gillman.Daniel@bls.gov] 
Sent: Tuesday, December 18, 2012 8:38 PM
To: Makx Dekkers; Public GLD WG
Cc: Sandro Hawke; Phil Archer
Subject: RE: Referencing FOAF
 
Makx et al,
 
This issue is one that is near and dear to my heart, so I want to weigh 
in.  I think the only option that makes sense is #1 for the following 
reasons:
 
1)      Trying to establish some authority or process for declaring “good” 
vocabularies is a non-starter.  One person’s  “good” won’t be everyone’s, 
and there are always going to be quirky local reasons for choosing one 
vocabulary over another.  An example from my business (national 
statistical office)  is industrial classification systems.  These are 
vocabularies in the GLD sense, and there are many of them, including ISIC 
(International System for Industrial Classification).  A determination 
that ISIC should be used for all applications where an industrial 
classification is required would ignore the special needs of regional and 
national systems geared towards the specifics of those economies.  Same 
with declaring any one of the regional systems “good”.  So declaring 
“good” is problematic.
2)      When a vocabulary is referenced or used, mostly it is with the 
concepts in that vocabulary defined at the time of use.  But, for any 
popular vocabulary, over time changes will be made.  Concepts are 
redefined, split, or combined.  New concepts are incorporated.  But, none 
of those changes should invalidate the use that was made before the 
changes.
3)      It is rare that no existing vocabularies will suffice for the 
needs for some problem, meaning creating one’s own vocabulary is rarely 
needed
 
If we were to recommend the creation of a catalog of vocabularies, this I 
believe would solve many of the problems described below.  First, any 
time-stamped vocabulary could be registered, rendering the problem of 
updates moot.  Second, a catalog will support discovery, and the problem 
of knowing which vocabulary to use and whether there are any relevant 
possibilities will be much easier to solve.  The use of a catalog will 
substantially reduce or eliminate the risk that vocabularies will be 
over-written and invalidate data.  Third, the issue of conceptual overlap 
among  similar concepts across vocabularies can be recorded, enabling 
developers to map across vocabularies and provide deeper semantic links 
across data.
 
I submitted 3 documents early in the GLD process that address these 
issues.  I updated the available versions, and they are located at
1)      
http://www.w3.org/2011/gld/wiki/File:Open_Government_Vocabualries_-_Registration_Procedure_v03.doc

2)      
http://www.w3.org/2011/gld/wiki/File:Open_Government_Vocabualries_-_Content_Model_v02.doc

3)      
http://www.w3.org/2011/gld/wiki/File:Open_Government_Vocabualries_-_Registration_Model_v04.doc

 
The first and third documents are especially relevant for this discussion.
 
Unfortunately, I will not be able to join the call on Thursday, but I can 
join during January (3rd or 10th).
 
Yours,
Dan
 
 
 
From: Makx Dekkers [mailto:mail@makxdekkers.com] 
Sent: Tuesday, December 18, 2012 11:03 AM
To: Public GLD WG
Cc: Sandro Hawke; Phil Archer
Subject: Referencing FOAF
 
Dear all,
 
There was a short discussion in the GLD call two weeks ago (
http://www.w3.org/2011/gld/meeting/2012-12-06) about referring to other 
people’s vocabularies. Here are some of my thoughts on this issue.
 
In earlier work that I was involved in, this issue has come up a couple of 
times. From those discussions, I remember three potential strategies:
 
1.       Re-use existing vocabularies irrespective of how they were 
developed and who is responsible for them. This has the advantage of 
maximum re-use, but of course the risk of using stuff that will disappear 
or be modified in uncontrolled ways, making your instance data invalid or 
undefined. 
 
2.       Re-use existing vocabularies that are somehow deemed to be 
“good”, e.g. well-defined, well-maintained or owned by a trusted entity. 
For this, you need a set of criteria that determine what is “good” and 
what is not. This could be purely a set of local criteria, but you might 
also consider a set of globally accepted criteria. One of the ideas that 
I’ve heard was that there could be a Community of Vocabulary Owners that 
would agree on good practice in the form of a common set of maintenance 
and persistence policies, which could include the kind of commitments like 
the one between DCMI and FOAF (http://dublincore.org/documents/dcmi-foaf/

). The advantage is that you would have some level of confidence that the 
vocabularies involved in this community would not disappear or break; the 
disadvantage is that such an approach takes time and effort in consensus 
building.
 
3.       Don’t directly re-use anything, but create parallel classes and 
properties in your own namespace with appropriate sameAs or subClass and 
subProperty declarations referring to other vocabularies as the 
alternative to re-use. I’ve heard the argument “Our project/service is 
going to be around longer than <fill in an organisation that maintains a 
vocabulary>” to argue for this approach. The advantage is that you’re not 
dependent on someone else’s policies or credibility, but I don’t think it 
will help the wider objectives of Linked Data. You’re moving the pain to 
the consumers who will need to resolve all these sameAs etc. relationships 
for incoming data to figure out that abc:title is really the same as 
xyz:title because they are both sameAs dc:title.
 
I had the impression that in the meeting it was suggested that W3C 
specifications may not want to refer to FOAF because it is outside of W3C 
which feels like going for option (3) – not re-doing FOAF of course, but 
in the sense of bringing existing FOAF under the W3C umbrella and 
associated policies. I hope that is not the general answer.
 
Makx.
 
 

Makx Dekkers
makx@makxdekkers.com
+34 639 26 11 46