From: Caleb Clausen <vikkous@...>
Date: 2006-03-25T09:04:48+09:00
Subject: Re: Suggestion for Ruby quiz

On 3/24/06, itsme213 <itsme213@hotmail.com> wrote:
> Integration of OWL with Ruby
>
> ######################
>
> OWL (Web Ontology Language) has several interesting capabilities, including:

Aside from the quizzy possibilities, you've made me curious about OWL
itself. I've never heard of OWL before, but it seems pretty
interesting. I'm trying to learn more now. Part of my interest is that
OWL resembles in some ways my pattern-matching language, Reg. It seems
that they address somewhat different areas, but there is perhaps quite
a lot of overlap.

From what I'm seeing right now, OWL is, unfortunately, XML-based.

> - Define a (possibly anonymous) class using property expressions
>    DarkChocolate = Dark & base_material is a Chocolate
>    Dark = (any Thing) with brightness = Low

So, in Reg this might be:

Dark = item_that.brightness==Low
DarkChocolate = item_that.base_material.is_a?(Chocolate) & Dark

alternately:

DarkChocolate = -{:brightness=>Low, :base_material=>Chocolate}

> - Class definition can be incremental and federated
>    Vehicle = ....
>    ...
>    Vehicle = ....

Uhh, you left too much out for me to make much sense of this.... but
it sounds like Ruby's open classes?

> - Classification
>    Determine if arbitrary object is member of class by checking properties

How would this differ from the DarkChocolate example above?

> - Equivalent | Disjoint | ...
>    Assert that two separately defined classes always | never have the same
> members

It sounds cool. And I have absolutely no idea how it could be done in my system.

> Tons of info on OWL on the web. One tutorial at
> http://www.cs.man.ac.uk/~horrocks/ISWC2003/Tutorial/

A page full of links to powerpoint and pdf files. I'm too ill today to
want to deal with that.... maybe tomorrow. I'll google about a bit for
this.

> One might even find some intriguing links between some of OWL's features and
> Ruby with duck typing, open classes, method_missing, dynamic mix-ins, etc.
> (See http://gigaton.thoughtworks.net/~ofernand1/DeepIntegration.pdf)
>
> An example of integrating OWL and Ruby, adapted from the above URL:
>
> class TeachersChild < OWL::Thing
>
>   defined_with_query some_expression_or_block_or_string
>
>   def misbehave
>     raise "Teacher's kids never misbehave"
>   end
>
> end
>
> obj1 = OWL::Thing.new (properties which may qualify as TeachersChild)
>
> obj1.misbehave # dynamically pick up TeachersChild#misbehave
>
> ExternalOWLTool.process obj1 # external reasoning tools

In Reg, classes (in the OO sense) and patterns (queries on objects)
aren't the same thing. So, this example really blows my mind. This is
really cool, and I like it. But I'm a bit unclear about this line:

obj1.misbehave

Am I correct in assuming that it raises the exception if
TeachersChild===obj1? If so, then what happens if obj1 is also a
ProblemChild that (mis)behaves differently?