[xtm-wg] Suggested public topic: "singleton"

["Nikita Ogievetsky" <nogievet@cogx.com>]

There have been several proposals on how to link
association with a topic link.
1)turn association into a topic
2)bring "id"-s on associations into the standard
3)add "topic" attribute on associations

I have reservations against all three suggestions.
Firstly, suggestion 1) depletes (as far as I am concerned)
the main concept of TopicMaps, which is:
"anything whatsoever" can be a topic.
And topic's participation in associations is just another piece of
information about a topic.

>From this point of view topic "marriage" participates in
association between "husband" and "wife" by playing role of the subject of
this association.

It can be expressed by means of "type" attribute on association or
adding an assocrl with type="this-assoc-subject" or
"topic-this-assoc-is-instance-of"

Suppose you want to supply any additional information about
a particular marriage.
Then you create a topic corresponding to this marriage, let's say
"marriageAtoB".
This "marriageAtoB" is of course of type "marriage".
Now the marriage association between A and B has a narrower subject of
"marriageAtoB".
As simple as that.

There is one peculiarity though:
Only a single association in a given scope can reference this topic.
This can be achieved by adding "singleton" to the super-types of
"marriageAtoB"
If there are two associations pointing to the same singleton type in the
same scope, they should be merged.
<topic id="marriageAtoB" types="marriage singleton">..</topic>
<assoc type="marriageAtoB">
..
</assoc>
or
<topic id="marriageAtoB" types="marriage singleton">..</topic>
<assoc>
<assocrl type="this-assoc-subject" href="marriageAtoB">
..
</assoc>

------

Suggestions 2) 3) above yield to jeopardizing integrity which is clear from
the following:
2)
<topic id="t2" types="some-other-assoc-type">
<locator href="a" type="is"/>
</topic>
<topic id="t1" types="some-assoc-type ">.</topic>
<assoc id="a" type="t1">...</assoc>
3)
<topic id="t2" types="some-other-assoc-type">.</topic>
<topic id="t1" types="some-assoc-type ">.</topic>
<assoc topic="t2" type="t1">...</assoc>

Integrity is broken in both cases if
Topic "t2" is not an instance of "t1"

So having simultaneously both {id and type} or {topic and type}
on association (or on any other non-topic xtm element)
is a very subtle matter and can not be used without
rigorous xtm schema constructs (to be defined yet).

Thanks,
Nikita.


-------------------------- eGroups Sponsor -------------------------~-~>
GET A NEXTCARD VISA, in 30 seconds!  Get rates 
as low as 0.0% Intro APR and no annual fee!
Apply NOW!
http://click.egroups.com/1/9332/4/_/337252/_/971116004/
---------------------------------------------------------------------_->

To Post a message, send it to:   xtm-wg@eGroups.com

To Unsubscribe, send a blank message to: xtm-wg-unsubscribe@eGroups.com