Re: SV: SV: FW: [plcs-dex] Unique constraints -> identification and versioning

[David Price <david.price@eurostep.com>]

Hi Mats, See below for two replies. Cheers, David

On Tuesday 19 December 2006 09:38, mats.nilsson@fmv.se wrote:
> Hi David,
>
> This is one of your examples of a "class.id URI";
>
> >> urn:iso:std:iso:ts:10303:-1017:ed-1:tech-taxonomy:Part
>
> If I understand you correctly, you suggests to include both the URI for the
> RDL ("urn:iso:std:iso:ts:10303:-1017:ed-1:tech-taxonomy") as well as the
> class identifier ("Part") in the 'external_class.id' (the 'id' attribute in
> the 'external_class' entity).
>
> I thought (see the last of my three slides) 'external_class_library.id' was
> going to be used for the URI of the RDL, and that the identifier within the
> RDL (i.e. 'external_class.id') only should contain the actual
> "classification" or "term" identifier, in your example "Part".

I don't think that works because of the other issues I mentioned (i.e. there 
are multiple ontologies involved and one ontology has to be identified as the 
context ontology). The context ontology is the most organization-specific 
ontology that uses the more general and standard ontologies. 
External_class_library is really the only entity type in PLCS that makes 
sense for that requirement and so I think there should be one instance of it 
that all the External_class entity instances point to (actually I don't think 
it's a big problem if there are multiple instances of External_class_library 
as long as they all refer to the same URI. So, if you've followed and agreed 
with the logic of requiring a context ontology then I think it's clear that 
the External_class.id needs to be the full URI.

For what it's worth, I think people have been assuming that "urn:oasis:plcs" 
was "the reference data library", when in fact in real-world usage that is 
unlikely to be the case. The RDL that is the context for an exchange is 
actually the ontology developed by the using organization with its extensions 
to the PLCS standard classes which is imported in read-only mode. Because of 
the flexibility enabled by the use of the OWL language, it's important to 
have that context ontology named in the exchange file. If you look at some of 
the OWL APIs you'll see that they often force you to supply an ontology when 
you'd think only a class is required as input. That's because the same class 
can have different subclasses *and* superclasses (not to mention properties) 
depending on how it is extended in using ontologies.

>
> Please help me understand if I've got things wrong! If someone else has an
> opinion, please help David help me...
>
>
> Now over to your question David. In my not so organized world (I call it
> FMV...) people use more than one term for the same concept (concept=class).
> OWL has the 'rdfs:label' element, which makes it possible to assign more
> than one term for each class. This is useful for me because the guys who
> drive helocopters and those who drive boats often have different
> terminology, and I can use this functionality to make them understand each
> other and the data they send. There is also this need to be "interoperable"
> within e.g. the EU Battle Groups or NATO joint operations, and then we
> swedes meet people that uses the word "lubricate" for what we call
> "smörja"...
>
> To accompish this I'd like to use a "meaningless" identifier for the
> 'external_class.id' field, e.g. "rd000453" (or with versioning
> "rd000453v1"), and then use the 'external_class.name' field for the
> readable classification (i.e. one of the available 'rdfs:label's in the
> RDL/OWL-file).
>
> This was what I meant by the question;
>
> >> David: How do you suggest the label used for
> >> classification should be identified in case there are multiple labels
> >> for the same class/RD?
>
> If I have both "lubricate" and "smörja" in the same class (that is a
> subclass of 'activity'/'task') with some unique id, I need to specify which
> one is used.
>
> Clearer? Or don't you see this scenario with synonyms and multiple
> languages (used for the same class/concept)?

I understand the question now. From what I've seen on the Semantic Web, the 
best practice is to use a (somewhat) human-interpretable name for the 
identifiers of classes in an ontology (within the limitations of what you can 
use in a URL or URI).  I agree that the use of rdfs:label is the proper way 
to specify the "name" of the class for use in browsers and GUI applications. 
However, I don't see any advantage in not following the Semantic Web 
practices. I've never really understood why anyone would want classes with 
ids like rd0049404 when they can have SerialNumber. The only rationale I've 
heard that made any sense to me was related to handling the uniqueness of ids 
but since we're engineering the reference data I don't think the cost in 
human understandability is outweighed by the small benefit of slightly easier 
uniqueness. That said, I also think that the PLCS RD should be broken up into 
sub-ontologies on a domain-by-domain basis for manageability, subsetting and 
to help with the overloading of terms.

All that said, I'm not sure that the External_class.name is really useful for 
transfering rdfs:label values. I'm not sure of the business need for that for 
a start. If the External_class.id is the full URI then that's sufficient for 
an application to process. If for some reason the rdfs:label is needed then I 
think name_assignment is the only way to handle the fact that a class may 
have multiple rdfs:label values for different languages. However, it seems to 
me it's better to keep all the labels in the ontology itself rather than 
duplicating them in the exchange file.

>
> Regards,
>   Mats
>
>
>
> -----Ursprungligt meddelande-----
> Från: David Price [mailto:david.price@eurostep.com]
> Skickat: den 18 december 2006 18:05
> Till: plcs-dex@lists.oasis-open.org
> Ämne: Re: SV: FW: [plcs-dex] Unique constraints -> identification and
> versioning
>
> Hi Mats, a few replies follow (although I'm confused by one question.
>
> On Monday 18 December 2006 07:51, mats.nilsson@fmv.se wrote:
> > Questions below...
> > Happy for opinions!
> >
> > Regards,
> >   Mats
> >
> > >> David: Could you please give an example of what an (external) class.id
> > >> URI could look like?
>
> It would be a URN or a URL depending on what organization defines it the
> class and the approach they happen to have adopted. It would be the compete
> URI for the class though it's technically only the identifier and so may
> not be sufficient for location (e.g. if it's a URN then some other means
> would have to be established for an application/user to find more info
> about the class ... for example, an organization might have to buy an ISO
> standard). Examples could be:
>
> urn:iso:std:iso:ts:10303:-1017:ed-1:tech-taxonomy:Part
>
> http://schema.omg.org/spec/UML/2.1/ParameterDirectionKind
>
> http://www.madeupdod.mil/ActivityOntology#Training
>
> > >> David: How do you suggest the label used for
> > >> classification should be identified in case there are multiple labels
> > >> for the same class/RD?
>
> I don't understand what "the label used for classification" means. Can you
> rephrase the question or explain that phrase?
>
> Cheers,
> David

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