Hi Matthew, (01)
You don't have to use the RDF flavour of OWL if you don't want to. There is
an OWL XML approach that is a bit simpler. (02)
In my experience of implementing this stuff, the problem lies more in the
use of triples than any kind of flavour of logic. Triples are convenient for
some sorts of data and a pain for others. It just so happens that for
ISO15926 and IDEAS, where we can have relationships to relationships, and
classes of classes of classes of relationships, RDF starts to get a bit
clunky. You can make it work, but it doesn't look very nice. (03)
That said, there are some really high performance triple stores around now,
so even the clunkiest RDF can be useable. (04)
Ian (05)
-----Original Message-----
From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Matthew West
Sent: 15 December 2010 19:50
To: '[ontolog-forum] '
Subject: [ontolog-forum] FW: [ontology-summit] Invitation to a brainstorming
call for the 2011 Ontology Summit (06)
[reposted here as requested by Peter] (07)
Dear Ian, (08)
> I'm constantly amazed at the passion that OWL seems to arouse. (09)
I am surprised at the strength and vigour of John's objections too, but I
think you are missing some of what is objected to. (010)
> OWL and the OWL
> 2 profiles are simply fragments of FOL with useful computational
properties.
> I'm surprised that we can get so excited about decidable fragments. I'm
even
> more surprised that someone who apparently likes FOL "hates" these
particular
> fragments. (011)
MW: Well if OWL was just an abstract syntax for these fragments I doubt if
anyone would be half as excited. What I think causes a collective groan
amongst those that have been around for several decades in this space is the
XML implementation on top of RDF. It is like inventing a square wheel when
you have a round one sitting in the corner (SQL) and then layering something
uncomfortably on top of it. (012)
Regards (013)
Matthew West
Information Junction
Tel: +44 560 302 3685
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matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
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http://www.matthew-west.org.uk/ (014)
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>
> I can easily understand why you and others might believe that OWL is too
> restricted for what you want to do, and why you might want to use full
FOL.
> Please go right ahead -- I won't be in the least offended. I don't see how
OWL
> would interfere with such an endeavour, and I would have thought that it
might
> even help as you can trivially extend OWL ontologies with arbitrary FO
axioms.
> In fact, you could think of OWL as being a design pattern, which you
> apparently like, as opposed to a fragment, which you don't like.
>
> Regarding the other techniques you mention, it is true that they can be
used
> to address some of the problems associated with computational complexity
> (where we can think of semi-decidability as being a very high complexity
> class). Modern OWL reasoners already employ many of these techniques. Of
> course we can, by definition, never "deal with" these problems, and
ontology
> languages with high computational complexity will always suffer from some
lack
> of robustness, i.e., relatively small changes in the ontology and/or data
may
> result in performance "falling off a cliff". This was the motivation for
the
> definition of the various OWl profiles: if a given application requires
some
> guarantee of robustness, then they can obtain it by staying within a
suitable
> profile. Note that the syntactic definition of profiles is crucial here,
> otherwise one risks deciding membership of the profile being an
intractable
> problem in itself.
>
> Coming back to the OWL -v- FOL question, I think that much of the
"problem"
> arises from fundamental differences in how we view the design and use of
> ontologies. Many of the ontologies I see are extremely simple (in fact I
often
> find myself being asked to defend the unnecessary expressive power of OWL)
and
> perhaps wouldn't pass muster if examined by a formal ontologist. However,
they
> may still be found to be an extremely useful piece of an application, even
if
> only a rather small piece. I tend to see this in a positive light -- we
are
> raising the profile of and exploring applications for ontologies.
Hopefully
> you can try to see OWL in a similar light -- it is raising the profile of
> ontologies, encouraging the use of (a fragment of) FOL as an ontology
> language, and providing you with a ready source of "customers" ripe for
> "upgrading".
>
> Regards,
> Ian
>
>
>
>
>
> On 10 Dec 2010, at 10:57, John F. Sowa wrote:
>
> > Ian,
> >
> > Before saying anything else, let me emphasize that I believe the work
> > on algorithms, complexity, and decidability by you and your colleagues
> > is very high quality and very important for computer science.
> >
> > But the sentences at the end of your note explain why *I hate OWL* :
> >
> >> In fact, it can be shown that query answering in OWL 2 RL [Rule
Language]
> >> is possible in time that in the worst case increases only polynomially
> >> with the size of the data. In *this* sense, OWL 2 RL really is less
> >> (computationally) complex. However, as I mentioned above, the price
> >> users pay for this is an *increase* in syntactic or cognitive
complexity.
> >
> > By syntactic complexity, I realize that you are talking about something
> > much more fundamental (and cognitively much harder for people to learn)
> > than the angle brackets. But knowledge acquisition has always been
> > the major bottleneck in AI and the SW. Anything that increases the
> > "cognitive complexity" is a bad step in the wrong direction.
> >
> > As Dean said,
> >
> >> I find that in the classes I do teach, the students are very concerned
> >> about complexity in the computational sense...
> >
> > But there are many ways of dealing with computational complexity while
> > actually *reducing* the cognitive complexity:
> >
> > 1. Design patterns. Every programming language is undecidable, but no
> > programmer would ever ask for less expressive power. Instead, they
> > have developed *design patterns* for systematic ways of using their
> > languages in ways that are known to be safe and efficient.
> >
> > 2. Hybrid systems. The original DLs were packaged as hybrids with
> > the DL component designed for efficient classification and a more
> > expressive language (rule-based, full FOL, or even arbitrary
> > procedures) were used to achieve the required expressive power.
> > And design patterns (or something similar) can be used for the
> > more expressive part of the hybrid. (The RL option of OWL doesn't
> > address the main reason why people use hybrids: they need more
> > expressive power, not less.)
> >
> > 3. Dynamic algorithm selection. Cyc has developed the largest formal
> > ontology on the planet, but CycL imposes no restrictions on the
> > expressive power. Instead, they use dynamic methods for selecting
> > appropriate algorithm(s) for each problem or subproblem they
> > encounter. Similar strategies are also used for the systems that
> > compete on the Thousands of Problems for Theorem Provers (tptp.org).
> >
> > 4. Knowledge compilers. For many applications, it's possible to do
> > a *static* selection of the algorithms: Map the very expressive
> > languages (such as CycL and others) via appropriate design patterns
> > to forms can be processed efficiently by known algorithms.
> >
> > I'm sure that you know the references for these methods, but for
> > other readers, I include some in the following article:
> >
> > http://www.jfsowa.com/pubs/fflogic.pdf
> > Fads and Fallacies About Logic
> >
> > At the ICCS 2010 conference, Boris Motik gave a good presentation
> > about adding finite graph models to OWL in order to broaden its
> > expressive power while preserving decidability.
> >
> > I certainly like the idea of supporting graphs, but not the idea
> > of adding more cognitive complexity to an already overstuffed
> > language. Instead of stuffing more into OWL, why don't you ask
> > some of your students to do research on methods such as #1 to #4
> > above to find ways of *reducing* the cognitive complexity?
> >
> > Other talks at ICCS described more efficient algorithms for
> > Formal Concept Analysis (FCA), which generates consistent lattices
> > from source data that is cognitively extremely simple.
> >
> > That would be another excellent topic for your students: design
> > hybrid systems that combine an FCA-style of hierarchy with automated
> > or semi-automated methods for supporting additional expressive power
> > at varying levels of complexity up to the level of CycL.
> >
> > Cognitive complexity is killing the Semantic Web. As a result,
> > people are building their own hybrids that add very scruffy methods
> > to OWL or RDFS or RDFa -- thereby destroying the decidability that
> > the OWL restrictions were designed to support.
> >
> > The four techniques above (or something similar) would be an
> > excellent way to support Tim B-L's project for "Web Science".
> >
> > John
> >
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