[sc34wg3] revised draft Reference Model document N0298
Martin Bryan
sc34wg3@isotopicmaps.org
Fri, 12 Apr 2002 08:30:14 +0100
Steve
Let me try to make the case clearer as you seem to have missed the essence
of it. The case I am thinking of is the one where the occrl attribute has an
implied value (i.e. the GI) which is associated via the type attribute with
the identifier of a particular topic (whose base names happen to serve as
its name, but the name part is irrelevant in this issue)
I don't claim to fully understand what an assertion is, or how the word
topic is restriced within SAM. When I use the word topic I mean the object
with a unique identifier that can be used to find out information such as
the base name and alternative names that can be displayed to users.
As I understand 13250 there is an implied link from the GI name (not itself
a topic) of the occurrence to the identifier of the topic referenced by the
type attribute. This topic identifies the role that the occurrence is
playing and, I therefore consider, should be used as the R node in your
model. You state that:
A: The name specified via the generic identifier can
become the subject of a topic (let's call it the
"name topic"). By means of a naming assertion, the
name topic's subject can be asserted to be a name of
the topic whose subject is the occurrence role.
This implies that the software has to create a "naming assertion" that
states that the name of the occrl is the name of the GI. But this loses the
fact that the type attribute states clearly which topic contains the naming
assertions associated with the occrl.
As Graham Moore has pointed out there is a problem with SAM in that it uses
names as a replacement for identifiers. My problem is that I think (possibly
mistakenly) that the identifier of the topic pointed to by the type
attribute of an occurs element could also find itself being used as an
assertion in some other context. Yet your rules would make this impossible.
You state "It's logically impossible for a single subject to be any
combination of them." This implies that there needs to be two of what you
call subjects if the same topic is being used as both a role of an
occurrence and as an assertion in another operation. I am trying to clarify
under what conditions a uniquely identified 13250 topic can be represented
by more than one node type in a SAM.
Martin
----- Original Message -----
From: "Steven R. Newcomb" <srn@coolheads.com>
To: <sc34wg3@isotopicmaps.org>
Cc: "Patrice Ossona de Mendez" <pom@ehess.fr>; "Pascal Auillans"
<pascal.auillans@mondeca.com>
Sent: Thursday, April 11, 2002 4:47 PM
Subject: Re: [sc34wg3] revised draft Reference Model document N0298
> "Martin Bryan" <mtbryan@sgml.u-net.com> writes:
>
> > I'm confused about Steve Newcomb's assertion that:
> >
> > * Any node that serves as the R end of any CR arc:
> >
> > * MAY serve as the R end of any number of CR arcs, and
> >
> > * CANNOT serve as the A end of any AC or AP arc, and
> >
> > * CANNOT serve as the P end of any AP arc, and
> >
> > * CANNOT serve as the C end of any CR, Cx, or AC arc.
> >
> > The subject of such a node is always a role (or,
> > using the jargon established in HyTM, a "role
> > type").
>
> > How does a HyTM occurs element that has both an
> > implied occrl (as indicated by the name of the
> > element) and a type attribute that indicates the
> > Topic whose names/characterizes the topic type create
> > a node that Cannot serve as the A node of any AC or
> > AP arc? Surely there is nothing in ISO 13250 that
> > stops a topic being used to name both a role and an
> > assertion.
>
> Caveat: I'm not sure what you mean when you speak of
> using a topic to name something. When you say
> "topic", do you mean <topic> element, or "node
> in a dRM-conforming graph"? For clarity, in
> the rest of this note, I'm adopting the
> convention that when I mean an instance of an
> SGML/XML element type, I surround its generic
> identifier with angle brackets. When I say
> "topic" without angle brackets, I mean "node in
> a dRM-conforming graph".
>
> Topics can *have* names, and a topic can *be* a name,
> but, in the dRM, only an *assertion* can associate a
> name with a topic. Topics don't name anything.
>
> Now I'll make some (possibly incorrect) assumptions
> about the question you've just asked, and ask it again
> in a way that I can answer:
>
> Q: "How can the generic identifier of a HyTM <occrl>
> element be reflected in a dRM-conforming graph?"
>
> A: The name specified via the generic identifier can
> become the subject of a topic (let's call it the
> "name topic"). By means of a naming assertion, the
> name topic's subject can be asserted to be a name of
> the topic whose subject is the occurrence role.
>
> > Surely there is nothing in ISO 13250 that
> > stops a topic being used to name both a role and an
> > assertion.
>
> I've repeated your last sentence, above, because I'm
> still trying to understand it. If you're saying that a
> single name can certainly be the name of both a topic
> whose subject is a role (i.e., an R-node) and of
> another topic whose subject is an assertion (i.e., an
> A-node), then I agree with you. But that possibility
> does not conflict with the dRM rules that you quote
> above, and that I will now restate more compactly
> below:
>
> * A single subject cannot be both a role and an
> assertion type (no R-node can also be a P-node).
>
> * A single subject cannot be both a role and an
> assertion (no R-node can also be an A-node).
>
> * A single subject cannot be both an assertion and an
> assertion type (no A-node can also be a P-node).
>
> Assertions, assertion types, and roles are three very
> different kinds of things. It's logically impossible
> for a single subject to be any combination of them.
> Their names, if any, are irrelevant. Anybody can
> assign any name to anything (or even, Orwellianly, to
> everything).
>
> > O298 states that "Each assertion asserts the
> > existence of a strongly-typed relationship between
> > some specific set of subjects of conversation" and
> > "The ontologies of Applications may include an
> > unbounded number of kinds of assertions." Given I
> > choose to use a topic whose name is "PublishedBy" as
> > the type of an occurrence element (so that I can have
> > documents published by people who are not defined as
> > topics) why cannot I also have an association that
> > asserts, where books are published by people
> > mentioned in the topic map, that the same topic
> > serves as the name of an association?
>
> It is perfectly OK for any number of subjects to be
> asserted to have the same name. (If we're using the
> naming assertion type defined by the SAM, which imposes
> the name-based merging constraint, then we'd better use
> different scopes for each of the naming assertions,
> lest these different subjects be incorrectly merged!
> But that's a SAM issue, not a dRM issue.)
>
> > Would this latter case have to be a role or would it
> > be, as I feel it should, an assertion?
>
> I guess I'm not sure what the antecedent of "latter
> case" is.
>
> -- Steve
>
> Steven R. Newcomb, Consultant
> srn@coolheads.com
>
> Coolheads Consulting
> http://www.coolheads.com
>
> voice: +1 972 359 8160
> fax: +1 972 359 0270
>
> 1527 Northaven Drive
> Allen, Texas 75002-1648 USA
>
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