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Re: LOD Constellation

From: Mike Bergman <mike@mkbergman.com>
Date: Mon, 06 Oct 2008 00:43:59 -0500
Message-ID: <48E9A59F.4020504@mkbergman.com>
To: Gong Cheng <gcheng@seu.edu.cn>
CC: public-lod@w3.org

Hi Gong,

Gong Cheng wrote:
> Hi Mike and All,
> Very interesting work! Class-level mappings are quite important to
> domain-independent data integration, e.g., search engines like Falcons.

Yes, we agree.  Falcons is consistently showing the right way to 
search and present this stuff.  I hope you see some new ideas 
about class mappings moving forward! :)

> And I still have some questions to be clarified. I've downloaded
> "class_level_lod_constellation.csv", which gives relations between
> ontologies rather than between classes. Are there any class-level mappings
> available? And, how do you obtain such mappings? Is it just based on
> explicitly stated axioms in ontologies, or based on any ontology matching
> algorithms?

Good questions and points.  I'm sure Fred will comment back as 
well in the morning and I hope others do as well on this ML.

You are correct that we do not have a comprehensive inventory of 
specific class mappings.  However, we *do* for those that involve 


As for the others shown on the LOD constellation diagram, we have 
ascertained there *are* class-level mappings but have not yet 
compiled the specific class-level assertions those non-UMBEL 
sources make.  That enumeration should be done.

Class-level mappings, because of their *generalizability* and 
*power*, need to be carefully done.  We have looked at automatic 
and semi-automatic methods for these mappings (an important 
personal and business focus), but in the end such class-level 
assertions are pivotal to quality and believability.  This 
current LOD constellation diagram is simply reporting the 
linkages with no comment on provenance or accuracy.

My own view is that, while some alignment or mapping algorithms 
might be helpful for screening or identification purposes, 
actionable mappings need to be QA/QC'ed by humans with provenance 
made clear.  Axioms and algorithms can help to identify and rank 
candidates, but should not be determinative.

However, saying that, our own UMBEL mappings have not taken that 
long and once made are easily reused with leverage.  IMO, it is a 
much less onerous task to do class-level mappings than instance 
ones.  (While a single class assignment may require more time and 
thought than an instance one, there are fortunately many fewer 
structural -- that is, class -- than instance relationships 
between most datasets.)

Of further caution is that once one moves beyond specific 
individual sameAs assertions to those involving entire classes 
the consequences of getting it wrong are greater.

But what we are seeing is that a few class connections can bring 
some really powerful inferencing.  Just getting a few right can 
be really powerful. . . .

Regards, Mike

> Regards,
> Gong
>> -----Original Message-----
>> From: public-lod-request@w3.org 
>> [mailto:public-lod-request@w3.org] On Behalf Of Mike Bergman
>> Sent: Monday, October 06, 2008 10:13 AM
>> To: public-lod@w3.org
>> Subject: LOD Constellation
>> Hi LODsters,
>> We are pleased to provide a LOD 'constellation' diagram [1] of 
>> class-level mappings within open linked datasets.  It is meant to 
>> accompany the LOD cloud diagram [2] that our community has been 
>> using for more than a year to great effect to educate the public 
>> about linked data.
>> Fred Giasson did all of the initial analysis behind the creation 
>> of this LOD 'constellation' diagram.  The input files behind this 
>> diagram are also available for download [1].
>> I have also provided a bit more background information and 
>> description of the importance of class-level mappings in a 
>> related blog post [3].
>> As that post tries to stress, we now have all of the essential 
>> infrastructure pieces for effectively promoting the linked data 
>> vision.
>> Pretty cool! and thanks to all of you for publishing the datasets 
>> and bringing linked data to this current inflection point.
>> Regards, Mike
>> [1] http://www/umbel.org/lod_constellation.html
>> [2] 
>> http://www4.wiwiss.fu-berlin.de/bizer/pub/lod-datasets_2008-09-18.html
>> [3] http://www.mkbergman.com/?p=457
Received on Monday, 6 October 2008 05:44:42 UTC

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