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

["Barker, Sean \(UK\)" <Sean.Barker@baesystems.com>]

Just to add a further strand to this discussion, Aristotle noted that definition goes by genus and species, that is, that a definition identifies what class of thing you are defining (genus), and how it differs from other things in that class (species). This has two implications.

Firstly, any single term in a taxonomy is determined by its context, that is, the full path from the root concept down to the term. In practice, humans infer the path directly from context, and homonyms do not cause any particular linguistic community any great problems (although it is a problem between different communities such as the UK and the US). In an OWL ontology, this will only cause problems if the reference to the term is ambiguous because the reference does not define the full context. (PS Tank is a particularly bad example to choose for homonyms - the term was originally a cover word from the 1914-18 war to fool the Germans that water tanks not AFVs were being delivered to the front line.)

Secondly, and embarrassingly obviously, the most important part of a classification is the classification criteria, that is, the (real world) criteria that one uses to decide whether what is falling on my head is fine rain, drizzle, mist, rain, spitting, heavy rain, a downpour, cats and dogs or sleet. The concepts are not "out there" waiting to be written down, but essentially an arbitrary choice of how many terms are needed to divide up the concept space and where the term boundaries are.  The term "essentially arbitrary" implies that we may choose to make different choices. In practice, the choices are based on the "forms of life" that we need to distinguish - in industrial terms, the processes. When, as you were going out of the door, your mother shouted at you "its raining", this was not a statement about the amount of water falling from the sky, but an injunction to put a coat on.

The idea that concepts are "out there" has been very influential (since at least Plato's "Republic"), but I suspect is a short cut we use in our thinking. In practice, the use of a term invokes many connotations - implied classifications and associations - which is why terminology debates are so confrontational and tediously long winded as these are teased out. My biggest concern in this whole discussion is that most of the definitions are being written using this "out there" thinking, rather than being explicit on when to use one term or when to use another in the same class. The danger is that we will produce a standard in geek speak - it works for the technologist, but not for the user.

I am now going on holiday until the new year, so merry Christmas and a happy new year.


Sean Barker
0117 302 8184

-----Original Message-----
From: mats.nilsson@fmv.se [mailto:mats.nilsson@fmv.se] 
Sent: 20 December 2006 08:43
To: plcs-dex@lists.oasis-open.org
Subject: SV: SV: SV: FW: [plcs-dex] Unique constraints -> identification and versioning

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Hi,

(See P.S. statement regarding the attachment and my approach to this discussion) (I've copied the section from David answer below on which I'd like to comment on)
 
>  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.

1. I'm not sure that the "Semantic Web best practice" is something we should pay to much attenention to, because imho PLCS Reference Data and Semantic Web ontologies are not that closely related, even though we use the same XML application (i.e. OWL) for the representation.

2. There will sooner or later be a case when homonyms appear in the same ontology. For now I have the two examples 'Tank' (container for liquid -or- combat vehicle) and 'Stone' (a unit of mesure -or- a primitive tool for emergency repairs). Both these examples are homoonyms likely to appear in the same domain (even though the 'Stone' example is a bit far-fetched...). In this case there still has to be a 'Stone(tool)'/'Stone(unit)' notation in order to separate them. A "meaninless" id string would bo more efficient.

3. You (David) did not comment on the real-world (...FMV...) fact that more than one word (synonyms) exists as "labels" for the same class. Which one should be used for the id? The use of the OWL "same_as" construct with separate classes (with identical definitions) is to me a more complicated way then using 'rdf:label' for the words and a "meaninless" id string for the class as a whole. 

4. In the "interoperability" or "multilingual" oriented world there could also be a reason to keep the 'rdf:ID'='external_class.id' as a "meaninless" id string, in order to allow "labels" in different languages and not beeing forced to use an English word as the identifier... Why not adopt (what I think is) the eOTD approach. What they do and what we do are quite similar when it comes to "concept management" (where concept=id+label(s)+definition). Their "Core Model" (and perhaps the "FMV concept management information model"... (attached)) might be something to take a look at.

I'm glad we got the discussion started! I hope more will join in... Reference Data is a key aspect to PLCS which in my opinion still is a bit too loosely defined.

Regards,
  Mats

P.S.
  The attached "FMV concept management information model" is still at a draft level (and has yet no descriptive text). Its purpose is to be the base for the definition of an XML based format for the representation of terminology used within FMV (and in the long run also for the Swedish armed forces). A project for addressing "concept management" will start at FMV in january with me as the projet leader. 

In order to be able to classify PLCS data correctly, the classifications should be based on a defined terminilogy. FMV doesn't have that today. In order for PLCS to work - this must be established! The aim of the project is first to create an infrastructure (data format, applications, processes, information/education and organisation), and then to launch the organisation and the work of creating a defined terminology. The infrastructure section of the project should be completed before summer! My ambition is, as far as it is possible, to use OWL in the same way as the OASIS PLCS TC specifies its use (something we'll soon have to agree on and do...) for our (FMV) terminology data format. 

This might explain some of my opinions expressed above and earlier...




-----Ursprungligt meddelande-----
Från: David Price [mailto:david.price@eurostep.com]
Skickat: den 19 december 2006 17:30
Till: plcs-dex@lists.oasis-open.org
Ämne: Re: SV: SV: FW: [plcs-dex] Unique constraints -> identification and versioning

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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