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Subject: Re: SV: SV: SV: SV: FW: [plcs-dex] Unique constraints -> identification and versioning
Hi Mats,
Please see my reply to Peter with an example of the problem I'm raising on
External_class_library ... hopefully it makes that issue clear. I do realize
identifiers is a separate discussion though, so comments below.
Basically I can't see why either Tank is named StorageTank if it's in the same
ontology with MilitaryTank or why simply putting a Tank class in a
StorageOntology as well as a MilitaryVehicleOntology are much of a problem.
Either approach is far better in every use case, for everybody involved, than
using RD934503932037 for the storage one and RD934503932037 for the other as
far as I'm concerned.
Cheers,
David
P.S. Did you all catch that I typed the same random number twice? If not, good
luck debugging a bad P21/P28 PLCS file.
On Friday 22 December 2006 10:11, mats.nilsson@fmv.se wrote:
> Hi David,
>
> I have at least three purposes of having this discussion with (mainly) you.
> First, I want to influence the development of RD in a way I find
> appropriate for PLCS and for FMV, secondly I want the discussion about RD
> to start among a wider audience so that this work gets going, and last, I
> want to learn more so I can make correct assesments of the work when it's
> started.
>
> I believe you have a deeper knowledge in OWL and its application to RD than
> I (currently) do. And if you, during this discussion manages to explain
> facts to me in a convincing way, I will have no problem in switching
> position in such matters. But we're not there yet... ;o)
>
> There is an advise saying;
> "It's better to be quiet and have people think you're an idiot, than to
> open your mouth and divert all doubts" For now I choose to ignore this
> piece of adwice and continue the discussion!
>
> See comments below...
>
> Regards,
> Mats
>
> P.S.
> A question; I think of the terms "concept" and "class" of beeing almost
> synonymns (meaining; "the idea you picture in your head when you hear a
> certain term"). Is this correct in your opinion?
I don't think I've used the term Concept. I've tried to always use Class since
for this discussion we're talking about OWL Classes for use as PLCS RD. I do
think they are related in that OWL Classes are one way that people organize
Concepts on a computer. I do tend to think of Concept as something in
someone's head though.
>
>
> -----Ursprungligt meddelande-----
> Från: David Price [mailto:david.price@eurostep.com]
> Skickat: den 21 december 2006 13:43
> Till: plcs-dex@lists.oasis-open.org
> Ämne: Re: SV: SV: SV: FW: [plcs-dex] Unique constraints -> identification
> and versioning
>
> Hi Mats,
>
> This reply is only concerned with the class id being a number vs words.
>
> Is your view that Class ids need to be meaningless based in the question of
> guaranteed uniqueness being simpler, or is there some other rationale?
>
> <mats>
> My view is based on my perception of the OWL-format having
> the 'rdf:ID' and the 'rdfs:label' elements, which makes it obvious
> (simpliest) to use the 'rdf:ID' as an ID, which in a perfect world would be
> unique and correspond only to one well defined concept/class, and to use
> the 'rdfs:label' for the term (in whatever language you prefere and
> allowing synonyms) used in the classification.
We don't seem to agree on "obvious" or "simplest":-) Perhaps it's my
background but things with ids like "RD9303930393" are neither obvious or
simple to me. But then I get confused when our project managers talk about
project 19303 vs project 17839 vs project 18773 which to me is exactly what
you're proposing we enforce through the OASIS PLCS standard.
>
> Of course, we can still use an ID that is interpretable to people
> understanding English, but I believe we should also then demand the use of
> 'rdfs:label" in parallell! This would of course make my FMV dictionary look
> a bit strange with some Ids beeing english words, and some meaningless
> strings (which would be the case when a concept/class isn't a part of the
> PLCS domain but exists in the FMV dictionary). It won't be easy for me to
> live with this but I believe it's not impossible!
I agree 1000 percent, that label should be used everywhere. It's what a human
user of the application should see. I don't think it's necessarily what the
human who's a PLCS implementor or RD developer are going to see though.
They'll see the ugly ontology and class ids and it's for their better
understanding that I think natural language names are especially useful.
>
> The use of 'rdfs:label' is a must in order to create a swedish dictionary
> that explains that a; "individnummer" is an "seriell identifierare" that is
> an "identifierare", and not having to say that; a "individnummer" is an
> "serial identifier" that is an "identifier". And yes, I forsee that we from
> Sweden will add swedish terms and add translations in swedish of the
> english definitions in the core PLCS reference data, i.e. of the entities!
>
> Another aspect of this is that we Swedes could then create an edition of
> the PLCS information model with all entities in Swedish, and the same for a
> number of other countries in their languages. Think of what this could mean
> in respect to promoting the standard... ;o)
> </mats>
I'm sure there are lots of Swedes who hope you share all that with the outside
world. It's very useful stuff.
>
> For example, this view seems to similar to how engineering orgs use Part
> Numbers to identify designs in their PDM systems. Do you hope to reuse PDM
> software in your org?
>
> <mats>
> No such plans.
> </mats>
>
> A second, perhaps implied, concern seems to be unhappiness at a choice
> having to be made about a natural language for the class id? My view is
> that reference data is simply more modeling in the domain covered by the
> PLCS schema and so the use of the same sort of conventions makes things
> simpler and more consistent. I can also see internal implementations where
> the reference data and EXPRESS are processed together to form a complete
> model (perhaps in OWL, perhaps in UML, etc) and consistency is useful in
> that case as well.
>
> <mats>
> Partly covered by the translation section above.
> </mats>
>
> On your suggestion that eOTD used numbers so PLCS RD should, I'd suggest
> that this shows a fundamental difference in approach and is indeed at the
> heart of the issue. The eOTD, and other similar standards, do use codes
> rather than words. I contend that all these coding approaches are the
> result of the earlier use of codes within relational databases where
> varying length strings are costly. People have simply taken an
> implementation tradeoff in RDBs and exposed them in the real world.
>
> <mats>
> Why don't we ask Gerry Raddack about this?!.
> </mats>
I don't think Gerry was around with the RDB developers started using codes.
It's probably based in some book from the 1980s on efficient RDB (or maybe
COBOL/IMS?) implementations. I know we used to think it was a good idea in
IBM to encode as much information in the names as possible, so we used codes
for lots of things too (e.g. all eng chgs orders that started with 10000 were
from manufacturing).
>
> However, for the PLCS scenarios we've chose
> to use a semantic language to expose the meaning of the term, and
> potentially enable reasoners over PLCS data, and which is Web-enabled via
> URIs. Therefore, the rationale for using codes doesn't apply in PLCS-land.
>
> My view is that Classes are not like Part designs or RDBs, Classes are part
> of a vocabulary (or ontology or taxonomy whichever term suits you)
>
> <mats>
> I prefere vocabulary or taxonomy rather than ontology.
> But I don't have a clear view of any of these concepts/terms...
> </mats>
OK. However, taxonomy is a subclass of ontology.
>
> and so using natural language makes more sense. I still can't imagine why
> anyone would prefer "RD0494049404" to "SerialNumber" as part of a URI that
> identifies a class in an ontology.
>
> <mats>
> I think people would prefere "serial number" to "SerialNumber" in their
> classifications, so you'd still need the 'rdfs:label', right?!
> An easy to use application that replaces/hides "RD0494049404" or
> "SerialNumber" with "serial number" is what I think people would prefere...
> </mats>
See above, it depends on which humans you mean ... application users
see "serial number" or "följetong antalen" (which I got from an online
English/Swedish translator) but application developers also
see "SerialNumber".
>
> To me, it's clearly more efficient to have a
> meaningful, if sometimes overloaded term, than a random number because
> people's time and potential errors costs more than any gain in computer
> processing. Maybe I'm missing something though?
>
> On your comments wrt OWL label vs equivalentClass - label is not used
> during reasoning but equivalentClass is, that's why it's useful ... not
> that label isn't useful.
>
> <mats>
> Is there any rules that guide "reasoning", or are you with the phrase
> "label is not used during reasoning" actually saying that "the current
> software tools doesn't use the label element"?
> </mats>
Annotations like label is not part of the formal semantics of an OWL ontology.
So, it's not just current tools, future reasoners cannot use them either.
>
>
> Cheers,
> David
>
> On Thursday 21 December 2006 07:53, mats.nilsson@fmv.se wrote:
> > Kind of what I suggested in the last of my examples then... ;o) Good we
> > agree!
> >
> > -------------------------------------
> > <class> -> Class id: RD039405951
> > Label: BEA serial sumber (en)
> >
> > Descriptive text (en);
> > "is a" -> a
> > <superclass> -> <RD039405950>
> > <..features..> -> applied to BEA assets according to BEA rules.
> > -------------------------------------
> >
> > Regards,
> > Mats
> >
> >
> >
> > -----Ursprungligt meddelande-----
> > Från: David Price [mailto:david.price@eurostep.com]
> > Skickat: den 20 december 2006 16:48
> > Till: plcs-dex@lists.oasis-open.org
> > Ämne: Re: SV: SV: FW: [plcs-dex] Unique constraints -> identification and
> > versioning
> >
> > Sean makes a very good point. There's a useful convention for defining
> > classes in an ontology used by some of the Oil and Gas folks that makes
> > Sean's comments explicit:
> >
> > A <class> is a <superclass> that <distinguishing features of this
> > particular subclass>.
> >
> > so in my example you'd have:
> >
> > A SerialNumber is an IdentificationCode that is one of a series assigned
> > for identification which varies from its successor or predecessor by a
> > fixed discrete integer value.
> >
> > I thought this was an excellent convention.
> >
> > Cheers,
> > David
> >
> > On Wednesday 20 December 2006 11:58, Barker, Sean (UK) wrote:
> > > 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
> > >
> > > *** WARNING ***
> > >
> > > This mail has originated outside your organization, either from an
> > > external partner or the Global Internet. Keep this in mind if you
> > > answer this message.
> > >
> > >
> > > 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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