RE: [xri] [Glossary] Definition of "Resource" and "Attribute" (long)

[Bernard Vatant <bernard.vatant@mondeca.com>]

Hello Drummond and al

Endless debate it seems ... For what it's worth, and between the lines,
two cents from topic maps land insight.

| At the F2F, we agreed to adopt the definition of "resource" supplied
by
| the URI spec. <snip definition/>
| 
| So at the f2f agreed that a resource was simply "anything that has
| identity". By this definition, data itself could be considered a
resource
| because you must be able to identify it or you can't use it.

Topic Maps use "subject" for "anything anyone cares to speak about",
which seems at first sight a definition less restrictive than "anything
that has identity". 
OTOH many people in TM community tend to think that TM "subject" is
equivalent to "resource" in the sense used by RDF and URI spec. 
In fact a subject, to be really "spoken about", has to be represented by
a topic in a topic map, and/or identified by the URI of a "subject
indicator". In both cases, it is identified indeed, either on a local
basis (topic in a topic map) or on more "universal" basis (URI). A
subject which is not identified can't be used or spoken about, so, IMO
at least, it barely "exists". Some notable Platonicians in TM community
would disagree with that, but from a pragmatic viewpoint, in our
information universe, existence means identity, so my proposal for
consensus would be:

TM "subject" = XRI - RDF - URI "resource" = "anything that is provided
with identity, in order to be spoken about"

| By this definition, then, resources are infinitely recursive - a
resource
| can contain a resource can contain a resource right down to the
smallest
| identifiable unit of data - a single bit.

Indeed. The universe tends to be fractal, so almost any subject
(resource) can be drilled down into aspects, components, elements,
attributes ...

| If you define a resource this broadly, then what we typically refer to
as
| an "attribute" - data whose purpose it is to describe another resource
(a
| person's hair color, a rock's weight, a book's page count) - must
itself
| be considered a resource.

Exactly. This is the "reification" issue, tackled both in RDF and Topic
Maps land. In TM, a typical topic "attribute" (called "characteristic"
there) is its name. The name can be considered a resource in several
ways (the character string, or the attachment of that string to that
topic etc.)

| If that's the case, we need another term that defines "that kind of
| resource which is not an attribute". In other words, a term for the
thing 
| an attribute describes - the person, the rock, or the book.
| 
| The classic computer science definition of this entity would be an
| "object".  (Immediately I shudder to think of having to include a
definition of
| "object" in our glossary.) But this introduces the question, "What is
the
| precise difference between an object and an attribute?" For example,
an
| object that stands alone in one context (say, a TelephoneNumber object
| that
| contains the attributes CountryCode, AreaCode, Number, Extension)
could be
| an attribute in the context of another object (say, a Telephone). In
fact,
| object-oriented methodologies typically classify attributes into two
| types:
| simple (attributes which do not contain other attributes) and complex
| (attributes which themselves contain attributes). The latter is often
| referred to as a data object. So are all attributes objects? All
objects
| attributes?

This is in fact a question of level of representation. You find the same
issue in metadata land. It's well known that data for X are metadata for
Y, and vice versa. If you want to be very generic as XRI, Topic Maps and
Published Subjects pretend to be, you have no choice: any generic
distinction like data/metadata, object/attribute, subject/property,
topic/occurrence is impossible, the distinction is always
context-driven. 

| This grates against common sense because there is a class of data that
is
| clearly the "endpoint" or "primitive" describing other objects - data
| values
| such as a person's hair color, a rock's weight, a book's page count.
This
| class of data is widely referred to as an "attribute". At the same
time
| there is another class of data (or data containers) that are the
"entity
| described by one or more attributes" - people, rocks, books. These are
| widely referred to as "objects". And while an object can be a complex
| attribute, it cannot be a simple attribute.

Yes, common sense is always context-driven. Every generic definition
grates against common sense, like logic and maths do. I used to teach
that stuff for quite a while, and the common difficulty of students in
maths is that it grates indeed ...

| This all boils down to 3 levels (if this is starting to sound like
| metaphysics, it's real close):
| 
| #1) Objects that exist independently of any other object, in a global
| context (call them independent objects).

From a pragmatic viewpoint, forget about those. As said above, any
subject (resource) is worth considering as soon as it is identified -
which means you have a background identification process or protocol (a
context). And I don't know what a global context means - a widespread
opinion is that only God is aware of the global context ... speaking of
metaphysics ... :o)

| #2) Objects that describe other objects, in a specific context (call
them
| complex attributes), and

Ontologists tend to call those classes and properties ...

| #3) Pure attributes which only describe an object in a single context
| (call them simple attributes).

... while those guys are instances of classes and properties

| Now the question is: are all three resources? With our original
definition
| of a resource as "anything that has identity", the answer might be
yes.
| But
| the more intuitive answer seems to be that "resource" only includes #1
-
| objects that exist independently of any other object.

This is an unsustainable definition IMO, since that "independence" is
the trickiest thing to define - if it exists at all. In my view of the
world, the class of such objects could as well be empty ...

| Why? My first argument would be that #2 and #3 don't actually fit the
| defintion of "anything that has identity" because an attribute -
either
| complex or simple - exists *only in the context of the object it
| describes*.
| Therefore it doesn't have it's own "identity". It exists only as part
of
| the
| identity of the object it describes.
| 
| Take, for example, a rock that weighs 3 pounds. This rock has
identity, if
| nothing other than the fact that it is the rock that weighs 3 pounds
(out
| of
| a pile of two rocks that weigh 3 and 5 pounds, respectively). But can
you
| say that "3 pounds" all by itself has identity? The NUMBERS and WORDS
have
| identity, but the actual value "3 pounds" is not ABOUT anything unless
it
| is put in the context of the rock it describes.

Well, I'm not sure this is correct. "3 pounds" might be defined as the
(equivalence) class of all objects that have that specific weight, and
as such it can be given identity.
OTOH the *assertion* itself "this rock weighs 3 pounds" can be given an
identity, in order to be able to attach information-metadata to it, like
"according to Drummond" or "by scales abc".
Things are not that simple ...
 
| As a friend of mine is found of quoting Alfred North Whitehead,
| "How many arguments could have been avoided if only the participants
had
| bothered to define their terms."

Sure. My favourite one along the same lines is more ancient, being
attributed to Confucius:

"Were I called to bring back order into the Empire,
my first concern would be to restore the meaning of words."

Cheers

Bernard

_____________________________________

Bernard Vatant

Senior Consultant - Knowledge Engineering
www.mondeca.com

Chair - OASIS Published Subjects TC
http://www.oasis-open.org/committees/tm-pubsubj 

_____________________________________