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Subject: individual space vs class space (was: Re: [xdi] Minutes: XDI TCTelecon Thursday 1-2PM PT 2009-02-12)

• From: Giovanni Bartolomeo <giovanni.bartolomeo@uniroma2.it>
• Date: Sun, 15 Feb 2009 20:11:51 +0100

Hello Markus, Drummond,

thanks for this input; I think this is a good way to explore:
information about instances of class should be somehow inside the xri.
However, this again clashes with (probably my wrong understanding of)
+x/+y/+x+y.
In fact, =giovanni+ball would mean =giovanni/\$has/+ball, thus
=giovanni/+ball/=giovanni+ball. Indeed, =giovanni+ball is an instance.
Well, this apparently might make sense, but consider a similar example:

=drummond/\$has/+friend

thus

=drummond/+friend/=drummond+friend

would =drummond+friend be an instance, like =giovanni or =markus?

=drummond/+friend/=giovanni
=drummond/+friend/=markus

In case not, what would be then the range of +friend?

The strange aspect is that things would work fine without +x/+y/+x+y!
Sorry, I'm probably still missing the real need to have this pattern
in our model.

Giovanni

At 20.39 13/02/2009, Markus Sabadello wrote:
Maybe the "class" ball should be +ball, and the "instance" ball should
be =giovanni+ball or =markus+ball or =drummond+ball or simply =+ball !

Markus

On Fri, Feb 13, 2009 at 7:37 PM, Giovanni Bartolomeo
<giovanni.bartolomeo@uniroma2.it> wrote:
Dear Drummond,

Thanks for these detailed minutes. Let me check if I've understood correctly:
In this example, let us assume that +ball/+color/+ball+color is a
valid dictionary entry (class definition).
Let suppose +aBall/\$is\$a/+ball (i.e. +aBall is an instance of +ball).
Since +aBall inherits properties from +Ball, I can say
+aBall/+color/+red, which is an "instance level" predicate.
But I cannot say +aBall/+color/+ball+color (right?)
Main question: would +aBall/+color/+aBall+color make any sense?
Second question: how to know that +aBall is "an instance"? \$is\$a might
also mean "subclassOf", right?

Thanks (and sorry for being so obsessive on this topic, countless
nights spent on this :-(,

Giovanni

At 06.34 13/02/2009, Drummond Reed wrote:
We next discussed another concern of Giovanni's with some "strange"
statements that can be made with \$has. This is related to this email:

http://lists.oasis-open.org/archives/xdi/200901/msg00054.html

It is the example about balls and their colors, where +x is +ball and +y is
+color. This produces the XDI RDF statement +ball/+color/+ball+color. But in
the same document we have also +ball/+color/+red. So you have two different
objects of the same predicate, which is fine in RDF, but one (=red) is an
instance of color and the other (+ball+color) is a subclass of color.

After some discussion, we realized that what was deceiving about these
examples is that they confuse the dictionary/class space (Bill would say
"T-box") from the individual/instance space ("A-box"). For example, in some