[sc34wg3] Towards TMDM 3.0

Lars Marius Garshol larsga at garshol.priv.no
Tue Feb 24 06:16:14 EST 2009

* Rani Pinchuk
> I am sorry to persist, this is still not clear to me.

If you don't understand I think you *should* persist. :)

> If I understand correctly, you say that usually item identifiers are  
> not
> used as subject identifiers, but when there are no subject identifiers
> we have to have something in order to merge, so we use item  
> identifiers.

Almost. I'm saying that item identifiers are usually what we use to  
identify topics, because usually there are no subject identifiers. The  
rest is right.

> I find this dangerous. Many topics might be merged by mistake (some  
> IDs
> might be popular defaults given by the Topic Maps engine. "1" for
> example. Other might be simply confusing choices. "bank" for example).

See below.

> I would actually prefer to merge by names which seems to me much more
> safe. Or, to use more sophisticated algorithms for merging (e.g. using
> NLP etc.).

Merging by name just isn't safe. Of course, you can do it sometimes,  
and sometimes you can use NLP, but we can't require this sort of thing  
in the standard.

> I understand from what you write that ID in XTM is an item identifier
> without the topic map IRI. Is this correct?


> At first, I thought that the item identifier includes the topic map  
> IRI,
> and therefore you could claim that the item identifiers are unique.

Item identifiers are absolute IRIs, so that if you download from


the file

   lmg - "Lars Marius Garshol".

the item identifier for the topic will be


(If you think this conflicts with my previous "Yes" above then please  
read your question one more time. The *ID* is not an IRI. The item  
identifier is.)

> All in all, I find that the model you describe above is very  
> confusing:
> item identifier actually identifies subject, but on a lower grade then
> subject locators and identifiers.

The TMDM says: "An item identifier is a locator assigned to an  
information item in order to allow it to be referred to." (Clause 5.1)  
So it really does identify the item, but ... well ... indirectly that  
does also identify a subject and we can't do anything to prevent that.  
But it really does refer to the item, and not what the item represents.

If you look at the item identifier above I think you'll agree that

  (1) Taken literally, it refers to the "lmg" topic.

  (2) It wouldn't be a huge stretch to say that in some sense it also
      indirectly refers to me.

--Lars M.

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