RE: [xtm-wg] parallel development of syntax and concept models

["Kal Ahmed" <kal@ontopia.net>]

Jim Farrugia wrote:
> JIM ALSO COMMENTS AND ASKS ...
>
>          5) There seem to be two particular ways to talk about just what
>          a topic is:  one is the familiar refrain that a topic
> must have at
> least one    of the following: a name, an occurrence, or a role played in
> association with   another topic. The other is the notion that a topic is
> in some sense both
>          a "node" and a "link" between nodes, which is what
> Michel and Ben
> seemed
>          to be suggesting today in their responses to my original
> questions.
>          (Below I refer to the former as "the first way" of understanding
> what a topic   is, and to the latter as "the second way" ....)  I
> think it
> is worthwhile to    keep these two ways of understanding a topic in mind,
> and perhaps come up       with an elegant synthesis of these two ways of
> looking at things.  Just a       thought.
>

It is also worth considering topic as binding point - an addressable object
which is assigned properties.

>          6) Is it fair to say that, in some sense, the topic link
> element form
>          is, informally speaking, the abstract box that houses
> only one of
> the three     pieces that make up a topic (in the sense of the
> first way of
>          understanding mentioned above)?  Specifically, one can find a
> topic name
>          in the topic link element form.
>

'In' ? Perhaps not. 'Attached to' or 'Associated with' might be a better way
of visualising it.

>          7) Also, in considering the dual nature of topic as both
> node and
> link,
>          (the second way of understanding what a topic is), is it fair to
> say that the   topic link element form, by itself, deals with only the
> notion of "topic as     node", and that it deals with this via
> the topic id
> or name ?  That is,
>          within the topic link element form, there is no mention
> of linking
> (between     topics and topics or between topics and
> occurrences).  Instead,
>          the two ways to think of "topic as link" are actually specified
> elsewhere.
>          Specifically, the link that connects topics with topics is
> specified in the     association link element form, and the link that
> connects topics with   occurrences is specified within the topic
> occurrence
> architectural form.  Is    this accurate? If so, it helps explain
> why this
> seems confusing (that there is  no linking done or specified within the
> topic link element form).
>

The topic link should be considered to be an aggregating link of topic
occurrences. In the Hytime syntax of 13250, this is explicit - the topic
link element <topic> is an varlink architectural element, if the topic has
occurrences. The link then consists of a number of anchors (the
occurrences), each of which point to one or more resources. In other words,
the spec uses 'link' to mean a collection of anchors - I think that you are
thinking of link as an individual anchor and that is causing some confusion.

>          8) And so, in summarizing these last thoughts, we can
> consider a topic
>          either as being made up of at least one of name,
> occurrence, role
> played ....   or as a "node/link" duality.   When we look in the spec at
> the topic link       element form, we can see just one piece of each of
> these ways of        understanding topic:  we can see the (optional) name
> in the first way of        understanding, or we can see, say, the
> topic id
> as representing the node in     the node/link way of understanding
> topic.  But we can't see, *in the topic link         element form itself*
> any of these other pieces of these two ways of     understanding.
> Specifically, in the first way of understanding, we don't find
> in        the topic link element form any mention of "topic as occurrence
> or role         played ..."; and in the second way of understanding, we
> don't find the notion
>          of topic as link.  To complete the picture of both
> understandings we
>          need to look outside the topic link element form itself.
>   Is all this
>          accurate?
>

If I understand correctly, the 'first way' of understanding a topic is as an
object with some characteristics. The 'second way' of understanding is as a
link which can be addressed (i.e. can be the target of another link).
It is important to not try and look for all of the aspects of the model in
the 13250 syntax. There are aspects of the model that are implicit. For
example, there is no syntactic link from a topic to the association for
which it defines one role or from a topic to the topic for which it defines
a type. This is a syntactic constraint, because maintaining redundant back
pointers is hard. However, there is a specific syntactic construct that
links an association role to the topic that describes it or a topic to its
type (as described by another topic) - the back-pointer is 'implicit' in the
syntax.

>          9)  The notion of "topic as link" in the "node/link" duality way
>          of understanding topics, seems to be partly dealt with
>          in the topic occurrence [element form?].  It is here where one
>          kind of link is treated - the link between a topic and
> its occurrence.
>          This same topic occurrence [element form] seems also to
>          deal with the second of the three pieces (i.e.,
> occurrence) in the
>          first way of understanding a topic - that a topic consists of a
> name, an        occurrence, or a role played .....   Is this accurate?
>

Again, the occurence is an anchor, and as such could be considered to be
part of the link.

>          10) The rest of the "topic as link" in the "node/link"
> duality way
>          of understanding topics, seems to be dealt with in the
>          association link element form.  (I have some questions about
>          just how such a link is established between topics using this
>          form, but ...)
>
>          What is still dangling for me is the missing piece of
>          "role played in association with other topics" in the first way
>          of understanding what a topic is.
>
>          11) What is the key insight behind the association role
> that makes
>          it, in the first way of understanding what a topic is, such a key
>          component?  And how does an association role relate to the
>          "node/link" way of understanding topics, if at all?

Think of it like this: If a topic has neither name, nor occurrence, and it
is not part of an association link with another topic, what is its purpose ?
(typing and scoping can be defined as associations). So at least one of
those three things is required for a topic to be meaningful (and probably
more than one of those things is required for it to be useful).

Cheers,

Kal


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