Hi Uldis, (01)
In the IDEAS ontology (www.ideasgroup.org) we used a naming pattern based on
(I think) original work done by PF Strawson and WVO Quine (Chris Partridge
would be able to give you a much better view of the philosophical origins). (02)
In a nutshell, the ontology is in two parts - objects & names (Chris uses
"ObjectSpace" and "NameSpace" but I don't want to confuse this with XML
namespaces, as the concepts are different). The objects constitute a
structural (mereology) and set-theoretic model of the domain of interest.
Each of these objects then maps over to one or more names in the names area.
Each name has a type (we call it NamingScheme), so we can distinguish
context for each name. (03)
Going down this route brings with it some hard work and some serious
un-learning that a lot of ontology developers don't like to get into, but I
think the payback is worth it. The challenge is that if names become a
secondary adornment on the objects, what then are our criteria for
identifying those objects ? For IDEAS (which was built using the BORO
method), the criterion is extent. This means that, in the case of
individuals, it is their spatio-temporal extent (if have two things which
occupy precisely the same space for the same time, they are the same thing).
In the case of classes, it is there members - if two classes have precisely
the same members (instances) then they are the same class. In both these
cases we would not create only one individual or class. The example Chris
likes to use is that of the class equilateral triangles. Its extent is
precisely the same as the class equiangular triangles, therefore we would
only create one class in IDEAS and give it two names. (04)
The potential for semantic de-confliction using this approach is incredible.
It allows you to be precise about how two things with the same name
descriptor differ. For example, if person A has a class "Table" and person B
also has one called "Table" you first need to work out if their extents are
the same. If not (e.g. if A thinks desks count as tables, but B does not)
then you create two classes, one called "table" in the person A namingscheme
and the other called "table" in the Person B namingscheme. You can then
create classes for the overlapping (all tables that are not desks) and
disjoint bits (desks). (05)
I've did some slides for a UK Govt Taxonomy group that covers some of this -
http://www.modelfutures.com/file_download/12/Taxonomy+and+Ontology+powerpoin
t97-03.ppt (06)
Cheers
--
Ian (07)
-----Original Message-----
From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Uldis Bojars
Sent: 27 October 2009 01:25
To: ontolog-forum@xxxxxxxxxxxxxxxx; SIOC-Dev
Cc: Simon Reinhardt
Subject: [ontolog-forum] Ontology modules and namespaces (08)
A good question [originally posted on semantic-web and public-lod lists]. (09)
Forwarding the conversation to Ontolog-Forum and SIOC-Dev lists as
their subscribers may also have interesting insights. (010)
Simon Reinhardt wrote: (011)
> Hi,
>
> It is becoming somewhat popular for large ontologies to be split into a
core ontology file and module ontology files (which import the core).
Normally each module then gets its own namespace for the terms defined in
it. I was wondering though if that is too complicated for users of the
ontologies. I have seen confusion of "sioc" and "sioct" (the prefixes for
the SIOC core and the SIOC Types module namespaces) and when such
vocabularies get higher adoption by people not so well versed with
ontologies I can see it happen a lot more often.
>
> So as an alternative I want to explore the idea of just using one
namespace shared between the core and the modules. The advantage would be
not having to guess which namespace to use. One disadvantage for the
developer(s) of the ontology is that a "local name" can only be used in one
of the modules or core, you can't use the same "word" under a different
namespace with a different meaning. Another disadvantage is that if you want
the terms to dereference to the ontology files they have been defined in
then you can only do that with a "/" namespace (and you have to set up lots
of redirects).
>
> My questions: What do you think of that idea? Can you see any other
advantages or disadvantages? Do you think several namespaces are not
confusing at all? And what are the main advantages to splitting up
ontologies into modules other than being easier to organise? Do they justify
a higher burden on the ontology users?
>
> Thanks,
> Simon
> (012)
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