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Fractal communities: Was: Rich semantics and expressiveness

From: Tim Berners-Lee <timbl@w3.org>
Date: Sat, 3 Mar 2007 18:27:49 -0500
Message-Id: <23ABE69B-B427-471C-BC83-03F53C3EE893@w3.org>
Cc: "SW-forum" <semantic-web@w3.org>, "West, Matthew" <matthew.west@shell.com>
To: "Hans Teijgeler" <hans.teijgeler@quicknet.nl>


On 2007-03 -03, at 05:19, Hans Teijgeler wrote:

> Folks,
>
> In this context I would like to bring up something that keeps  
> puzzling me.
>
> The W3C Semantic Web Activity Statement [1] starts with:
>
> "The goal of the Semantic Web initiative is as broad as that of the  
> Web: to create a universal medium for the exchange of data. It is  
> envisaged to smoothly interconnect personal information management,  
> enterprise application integration, and the global sharing of  
> commercial, scientific and cultural data. Facilities to put machine- 
> understandable data on the Web are quickly becoming a high priority  
> for many organizations, individuals and communities."
>
> This is great, and it is what we strive for. But it is puzzling how  
> this can ever be achieved without a universal, generic, data-driven  
> model and standard data to drive that model. What I see happening  
> is that everybody can and often does invent instances of owl:Class  
> and owl:ObjectProperty on-the-fly, and then seems to expect that DL  
> will be the band-aid that solves all integration problems. In order  
> to assist the reasoners all sorts of qualifications are added (re  
> OWL1.1), but to me it seems that when this is done, actually a  
> (rather private) data model is created again.
>
> Above statement envisages the "smooth interconnection" of a  
> plethora of totally different application domains. That is wise,  
> because we live in one integrated universe (domain), and nobody can  
> dictate where one subdomain stops and the other begins.

Rather than 'domain of discourse' , or set of things considered, I  
think of 'community', set of agents communicating using certain  
terms.  When one thinks in terms of domain of discourse, one tends to  
conclude that everyone who talk at all about a car (say) has cars in  
their domain of discourse and  so everyone must share the model which  
includes the single class Car.

It isn't like that though.  An agent plays a role in many different  
overlapping communities.  When I tag a photo as being of my car, or I  
agree to use my car in a car pool, or when I register the car with  
the Registry of Motor Vehicles, I probably use different  
ontologies.   There is some finite  effort it would take to integrate  
the ontologies, to establish some OWL (or rules, etc) to link them.

- Everyone is encouraged to reuse other people's classes and  
properties to the greatest extent they can.
- Some ontologies will already exist and by publicly shred by many,  
such as ical:dtstart, geo:longitude, etc.  This is the single global  
community.
- Some ontologies will be established by smaller communities of many  
sizes.

Why do I think the structure should be will be fractal?  Clearly  
there will be many more small communities, local ontologies, than  
global ones. Why a 1/f distribution? Well, it seems to occur in many  
systems including the web, and may be optimal for some problems.   
That we should design for a fractal distribution of ontologies is a  
hunch.  But it does solve the issue you raise.  Some aspects of the  
web have been shown to be fractal already.

Here are some properties of the interconnections:

- The connections between the ontologies may be made after their  
creation, not necessarily involving the original ontology designers.
- There is a cost of connecting ontologies, figuring out how they  
connect, which people will pay when and only when they need the  
benefit of extra interoperability.
- Sometimes when connecting ontologies, it is so awkward there is  
pressure to change the terms that one community uses to fit in better  
with the other community. Again, a finite cost to make the change,  
against a benefit or more interop.

> Hence the need for a universal model as a common denominator. But  
> it is striking that the word "interconnection" was used, rather  
> than "integration". Interconnection reminds me of EAI [2], so hub- 
> based or point-to-point, where Semantic Web integration (as I  
> understand it) involves a web-based distributed data base.

Yes, if web-based means an overlapping set of many ontologies in a  
fractal distribution.
In his fractal tangle, there wil be several recurring patterns at  
different scales.
One pattern is a local integration within (say) an enterprise, which  
starts point-point (problems scale as n^2) and then shifts with EIA  
to a hub-and-spoke as you say, where the effort scales as N.    Then  
the hub is converted to use RDF, and that means the hub then plugs  
into a external bus, as it connects to shared ontologies.



>
> Keeping in mind that, as I wrote before in this thread, application  
> systems store a lot of implicit data (or actually don't store  
> them), the direct mapping of their data to the SW formats will  
> cause more problems than its solves. They are based on their own  
> proprietary data model, and these are unintelligible for other,  
> equally proprietary, data models.
>
> The thing puzzling me is how the SW community can see what I cannot  
> see, and that is how on earth you can achieve what your Activity  
> Statement says, without such a standard generic data model and  
> derived standard reference data (taxonomy and ontology). But  
> perhaps not many SW-ers bother about the need of universal  
> integration, and are happily operating within their own subdomain,  
> such as FOAF.

So the idea is that in any one message, some of the terms will be  
from a global ontology, some from subdomains.
The amount of data which can be reused by another agent will depend  
on how many communities they have in common, how many ontologies they  
share.

In other words, one global ontology is not a solution to the problem,  
and a local subdomain is not a solution either.  But if each agent  
has uses a mix of a few ontologies of different scale, that is forms  
a global solution to the problem.

Tim.

>
> Can anybody enlighten me, at least by pointing to some useful links?
>

ummm   http://www.w3.org/DesignIssues/Fractal.html  to which I might  
add this explanation some time.



> Regards,
> Hans
>
> PS The above does not mean that I have no faith in the SW. On the  
> contrary, I preach the SW gospel. But I just want to understand  
> where it is moving to.
>
> [1] http://www.w3.org/2001/sw/Activity
> [2] http://en.wikipedia.org/wiki/Enterprise_Application_Integration
>
> ____________________
> OntoConsult
> Hans Teijgeler
> ISO 15926 specialist
> Netherlands
> +31-72-509 2005
> www.InfowebML.ws
> hans.teijgeler@quicknet.nl
>
>
>
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Received on Saturday, 3 March 2007 23:28:03 UTC

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