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Re: Terminology: How to call "IRI or blank node"?

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Thu, 08 Jan 2015 18:40:43 -0800
Message-ID: <54AF3FAB.2080407@gmail.com>
To: Holger Knublauch <holger@topquadrant.com>, "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>


On 01/08/2015 05:13 PM, Holger Knublauch wrote:
> On 1/6/2015 1:06, Peter F. Patel-Schneider wrote:
>> There still appears to be some disagreement.
>
> As Peter made it clear that he feels very strongly about this issue, I would
> like to follow up towards a resolution even though I think we could also delay
> the specific question until it comes back (in the context of :valueType).
>
> The remaining question to me is that if we mint our own property :valueType
> which of the following options is best (for the community):
>
> a) We make a clear statement in the documentation of :valueType that the
> following meaning is assumed (we can even state that this slightly deviates
> from its use in rdfs:range):
>
> - :valueType is empty -> no constraint
> - :valueType = rdfs:Resource -> IRI or blank node
>
>  From my experience if I look outside of the W3C WG microcosm, I believe the
> above would be best aligned with the current practice.

This is absolutely counter to the requirement that the working group must use 
rdfs:Resource in a way that abides by its meaning as defined in the RDF 
specification.

> b) We introduce another property :nodeType with values (:Literal,
> :BlankNodeOrIRI, :BlankNode, :IRI) and assume that :valueType = rdfs:Resource
> means unconstrained and people need to combine it with :nodeType), i.e.:
>
> - :valueType = rdfs:Resource (or empty) && :nodeType = :BlankNodeOrIRI -> IRI
> or blank node

This mints new terminology and thus does not run counter to the requirement 
that the working group must use rdfs:Resource in a way that abides by its 
meaning as defined in the RDF specification.

> Questions:
>
> 1) Peter, would option b) work for you, if a) doesn't?

I have no problem with option b) not abiding by the requirement that the 
working group respect pre-existing terminology.

> 2) Assuming I also state that I feel strongly about this, what does the WG do?
> Does this mean that we have a deadlock and no further progress can be made? I
> believe both view points are valid, so instead of simply putting a veto on the
> table, I think a proper process would be to at least allow others to speak up
> and have a vote, then re-evaluate whether the veto is still appropriate?
>
> BTW I can live with option b) but I am afraid we are exactly repeating the
> mistakes that other WGs have made in the past, by putting theory before
> practice. I predict this will be one of the issues that most users will find
> unintuitive and that we will have to explain to users over and over again
> (just like we now have to explain the weird semantics of rdfs:domain over and
> over again).
>
> Thanks,
> Holger
>
>
>>
>> I do not believe that the working group can use rdfs:Resource in any way
>> other than as the class of all resources.  The only exception would be in
>> situations where all classes have special behaviour, such as using classes
>> to control the operation of constraints.  This would have to be done in a
>> uniform manner, and the wording would have to be carefully chosen to ensure
>> that no confusion would arise.
>>
>> peter
>>
>>
>> On 01/05/2015 05:37 AM, Johnston, Patrick - Hoboken wrote:
>>> I agree. Can we put this one to bed and move on?
>>>
>>> We can't fix previous specs here, but we can ensure that the documents we
>>> produce are intellectually accessible and not needlessly esoteric. We're
>>> not trying to make Rdf popular, we're trying to help it grow up so that it
>>> can play compatibly with the web and data description languages it
>>> straddles. Popularity will come only if it is useful to the wider community
>>> and we can talk about it in terms of what it does rather than what it is.
>>>
>>> Patrick
>>>
>>>> On Jan 4, 2015, at 7:13 PM, Holger Knublauch <holger@topquadrant.com> wrote:
>>>>
>>>> I agree we should use the term "resource" consistently with other RDF
>>>> specs inside of our own specs. The target audience of those formal specs
>>>> is comparably small and average users will learn the shapes language
>>>> from other tutorials and example snippets anyway. The best approach
>>>> might be to avoid the term "resource" and use "IRI or blank node" in
>>>> suitable places.
>>>>
>>>> With the meaning of rdfs:Resource in the context of property ranges, I
>>>> believe we do have flexibility as long as we do not overload and reuse
>>>> the properties rdfs:range or owl:allValuesFrom. If we coin another
>>>> property (such as :valueType) then I believe we do have the freedom to
>>>> specify that *in the context of this property*, using rdfs:Resource
>>>> means "IRI or blank node", because this is the de-facto interpretation
>>>> that the majority of users will more easily understand. Just leave the
>>>> :valueType empty to mean "any node".
>>>>
>>>> I had sent the link to the Google trend for RDF in a previous email.
>>>> This is not the only evidence that RDF has not succeeded in attracting a
>>>> large user base. I believe if we want to relaunch interest in RDF then
>>>> we need to focus on its good bits and work around the things that did
>>>> not work well. Many design decisions in RDF Schema and OWL in particular
>>>> were made with other use cases in mind. Some naming decisions were
>>>> unfortunate including rdfs:Resource but also owl:ObjectProperty (the
>>>> term "object" is used in triples). For these reasons I am against a
>>>> general assertion that we must slavishly follow in the footsteps of the
>>>> previous RDFS/OWL specifications. Instead I suggest we try to keep our
>>>> documents as self-contained as possible, so that potential users and
>>>> implementers can understand the relevant background without reverting to
>>>> other complex and often contradicting specs.
>>>>
>>>> Holger
>>>>
>>>>
>>>>> On 1/4/2015 13:50, Peter F. Patel-Schneider wrote:
>>>>> There may be multiple communities in this discussion, but the working
>>>>> group exists in the W3C RDF space.  I thus feel very strongly that the
>>>>> working group must not produce documents that use core W3C and RDF
>>>>> terminology in ways counter to their meaning within W3C and RDF.
>>>>>
>>>>> peter
>>>>>
>>>>> PS: By the way, I don't particularly like this particular terminology.
>>>>>
>>>>>
>>>>>> On 01/03/2015 11:35 AM, Karen Coyle wrote:
>>>>>> In the email below I readily conceded that rdfs:Resource belongs to
>>>>>> the RDF
>>>>>> context and is specific to the definition given in that context. But
>>>>>> "resource" is a word that already belongs to a larger populartion
>>>>>> than RDF
>>>>>> standards. When we use the term we must be clear which context we
>>>>>> mean. We
>>>>>> cannot, however, limit our use to the definition given in RDF
>>>>>> documentation
>>>>>> unless we are only specifically referring to that meaning, and only
>>>>>> speaking
>>>>>> to a very narrow cohort.
>>>>>>
>>>>>> As I'm sure you're aware, prescriptive linguistics fail outside of
>>>>>> highly
>>>>>> specific environments. Not wanting to be part of a limited society, I
>>>>>> prefer
>>>>>> clarity of context.
>>>>>>
>>>>>> Relating back to something that came up between Peter and Arthur,
>>>>>> there are
>>>>>> indeed multiple communities in this discussion. There is also a broad
>>>>>> audience
>>>>>> range. As the Dublin Core community learned during its development,
>>>>>> adoption
>>>>>> of a standard is greatly aided by broadening, not narrowing, the
>>>>>> potential set
>>>>>> of users. I hope we can do the same here.
>>>>>>
>>>>>> kc
>>>>>>
>>>>>>> On 1/2/15 10:36 AM, Peter F. Patel-Schneider wrote:
>>>>>>> Resource is a term defined in several W3C documents.  In particular,
>>>>>>> RDF
>>>>>>> 1.1 Concepts and Abstract Syntax has a section on Resources and
>>>>>>> Statements,
>>>>>>> http://www.w3.org/TR/rdf11-concepts/#resources-and-statements, where
>>>>>>> resources are stated to be the things that are denoted by IRIs and
>>>>>>> literals (and blank nodes, too, but this comes later). Here is one of
>>>>>>> the places where "resource" is defined as the universal category.
>>>>>>>
>>>>>>> This working group is an RDF working group and is obliged to use words
>>>>>>> like resource in the way they are defined in the RDF specifications,
>>>>>>> unless there is no chance that the use of such words could be
>>>>>>> considered
>>>>>>> to refer to their RDF meanings.
>>>>>>>
>>>>>>>
>>>>>>> rdfs:Resource an IRI that is given a fixed meaning in a section of RDF
>>>>>>> Schema 1.1
>>>>>>> http://www.w3.org/TR/2014/REC-rdf-schema-20140225/#ch_resource.
>>>>>>> rdfs:Resource there defined as the class of everything. All resources
>>>>>>> are instances of this class.  The definition is made formal in a
>>>>>>> section
>>>>>>> of RDF 1.1 Semantics
>>>>>>> http://www.w3.org/TR/2014/REC-rdf11-mt-20140225/#rdfs-interpretations.
>>>>>>>
>>>>>>> This working group is similarly obliged to use IRIs like rdfs:Resource
>>>>>>> in the way they are defined in the RDF specifications.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> It is certainly the case that the RDF meaning of resource is different
>>>>>>> from the RDF meaning of rdfs:Resource.  However, both of these are
>>>>>>> vital
>>>>>>> parts of RDF, and have meanings in RDF that this working group is
>>>>>>> obliged to defer to.
>>>>>>>
>>>>>>>
>>>>>>> peter
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> On 12/23/2014 07:47 AM, Karen Coyle wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>> On 12/22/14 7:25 PM, Peter F. Patel-Schneider wrote:
>>>>>>>>> Agreed.  I did not provide any examples concerning problems that such
>>>>>>>>> misconceptions have caused.
>>>>>>>>>
>>>>>>>>> How about the recent discussion concerning "resource" in resource
>>>>>>>>> shapes
>>>>>>>>> as a proximate example?  How about the difference between
>>>>>>>>> "resource" in
>>>>>>>>> RDF and "resource" in several RDF APIs?
>>>>>>>>
>>>>>>>> The difference we've been discussing, as I've understood it, is
>>>>>>>> between
>>>>>>>> rdfs:Resource and "resource". The former is formally defined and one
>>>>>>>> should
>>>>>>>> abide by that definition when using rdfs:Resource. The latter is a
>>>>>>>> general
>>>>>>>> term in English with a less precise meaning, and, AFAIK, anyone can
>>>>>>>> give it a
>>>>>>>> meaning in their own API. There is no reason to assume that it means
>>>>>>>> the same
>>>>>>>> as rdfs:Resource. Nor that the word "thing" means the same as
>>>>>>>> owl:Thing. I
>>>>>>>> admit that I use the terms "resource" and "thing" frequently without
>>>>>>>> intending
>>>>>>>> their RDF meanings; in particular, "resource" is commonly used in
>>>>>>>> libraries
>>>>>>>> and archives to mean "the created resource which we are describing."
>>>>>>>>
>>>>>>>> It might be a good idea to avoid using "resource" in an RDF-related
>>>>>>>> context in
>>>>>>>> a way that might be confused with rdfs:Resource. It depends, as Irene
>>>>>>>> says, on
>>>>>>>> whether users in that context with be confused. I could definitely
>>>>>>>> imagine
>>>>>>>> using "resource" in a user interface for metadata creation, or a user
>>>>>>>> display.
>>>>>>>> My users will be totally unaware of the existence of rdfs:Resource.
>>>>>>>> "Resource
>>>>>>>> shapes" works for me. I'm not comfortable with a re-defining of
>>>>>>>> rdfs:Resource
>>>>>>>> to mean "an IRI or a blank node" because it already has a precise
>>>>>>>> definition
>>>>>>>> that is different from that. I don't know what the use is in the APIs,
>>>>>>>> but
>>>>>>>> it's possible that the use of "resource" does not cause confusion.
>>>>>>>>
>>>>>>>> kc
>>>>>>>>
>>>>>>>>>
>>>>>>>>> peter
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> On 12/22/2014 07:18 PM, Irene Polikoff wrote:
>>>>>>>>>> Peter,
>>>>>>>>>>
>>>>>>>>>> This is a an abstract theoretical statement not supported by any
>>>>>>>>>> specific real practical examples.
>>>>>>>>>>
>>>>>>>>>> We have had many years of practice. By "we" I mean software
>>>>>>>>>> professionals. In practice, multiple data models have been in use
>>>>>>>>>> for
>>>>>>>>>> a long periods of time - for example XML and relational databases to
>>>>>>>>>> name the most popular ones. These models do not make a point to talk
>>>>>>>>>> about the distinction between the data structures and things in the
>>>>>>>>>> world the data represents. Their lack of attention to this
>>>>>>>>>> distinction
>>>>>>>>>> has not prevented them from being hugely successful and used in
>>>>>>>>>> pretty
>>>>>>>>>> much every piece of software today.
>>>>>>>>>>
>>>>>>>>>> Further, I am not aware of any software professional who have ever
>>>>>>>>>> confused the data structures with the things they represent.
>>>>>>>>>> Every one
>>>>>>>>>> understands clearly and unambiguously that the information space is
>>>>>>>>>> just that - information. A graph with data about Dick Chaney is just
>>>>>>>>>> data, not the person. To my knowledge, no one have ever had a
>>>>>>>>>> misconception about it. Based on the experience to date, the
>>>>>>>>>> probability of anyone having such misconception in the future is
>>>>>>>>>> extremely low.
>>>>>>>>>>
>>>>>>>>>> I am certain there are challenges in creating a useful standard
>>>>>>>>>> specification, but this one seems to be the least of the issues.
>>>>>>>>>>
>>>>>>>>>> If you have examples of the real (not a casual colloquial speech)
>>>>>>>>>> confusion between RDF nodes as data and resources in the world as
>>>>>>>>>> things, I'd like to hear about them and learn about the problems
>>>>>>>>>> they
>>>>>>>>>> have caused.
>>>>>>>>>>
>>>>>>>>>> Irene
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> On Dec 22, 2014, at 8:31 PM, "Peter F. Patel-Schneider"
>>>>>>>>>>> <pfpschneider@gmail.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>> The danger is that one talks about a node when one means to talk
>>>>>>>>>>> about a resource, or vice versa.  This can be benign, if the
>>>>>>>>>>> misconception either is not important or can be easily fixed, or
>>>>>>>>>>> serious, if the misconception matters and is not easy to fix.
>>>>>>>>>>>
>>>>>>>>>>> When one is writing specifications, the only safe assumption is
>>>>>>>>>>> that
>>>>>>>>>>> misconceptions are matter and are not easy to fix, because one does
>>>>>>>>>>> not know the contexts in which one's terminology will be used.
>>>>>>>>>>>
>>>>>>>>>>> peter
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>> On 12/22/2014 04:59 PM, Irene Polikoff wrote:
>>>>>>>>>>>> So, let's say there is a theory and meta theory and even several
>>>>>>>>>>>> layers of it. There used to be a joke slogan in the OO community,
>>>>>>>>>>>> btw, "Anything you can do, I can do meta". And let's say, these
>>>>>>>>>>>> get
>>>>>>>>>>>> conflated.
>>>>>>>>>>>>
>>>>>>>>>>>> Who and what will such conflation impact negatively? What systems
>>>>>>>>>>>> and applications get broken? How will it change what people who
>>>>>>>>>>>> are
>>>>>>>>>>>> using the standards to build solutions are doing and how they are
>>>>>>>>>>>> putting the technologies to work?
>>>>>>>>>>>>
>>>>>>>>>>>> In other words why is this important and what parts are important?
>>>>>>>>>>>>
>>>>>>>>>>>> Irene
>>>>>>>>>>>>
>>>>>>>>>>>> Sent from my iPhone
>>>>>>>>>>>>
>>>>>>>>>>>>> On Dec 22, 2014, at 12:28 PM, "Peter F. Patel-Schneider"
>>>>>>>>>>>>> <pfpschneider@gmail.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> Being the same is a concept that needs clarification here.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Yes, "2"^^xs:integer is a literal and ex:two is a URI.  These
>>>>>>>>>>>>> cannot be the same in RDF because URIs, blank nodes, literals are
>>>>>>>>>>>>> disjoint.  However, ex:two can be required to denote an integer,
>>>>>>>>>>>>> which is a literal value.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Yes, there is no atomic name in the metatheory of RDF that stands
>>>>>>>>>>>>> for those nodes in an RDF graph that can be the subject of a
>>>>>>>>>>>>> triple
>>>>>>>>>>>>> in an RDF graph. But why does there have to be? One can always
>>>>>>>>>>>>> say
>>>>>>>>>>>>> "IRI or blank node".
>>>>>>>>>>>>>
>>>>>>>>>>>>> One could create such an atomic name.  One might use "entity" for
>>>>>>>>>>>>> this purpose.  However, one should *not* use rdf:Entity, as that
>>>>>>>>>>>>> would conflate the RDF theory (where one has names like
>>>>>>>>>>>>> rdf:Property, rdfs:Resource, and xs:Integer) and the RDF
>>>>>>>>>>>>> metatheory
>>>>>>>>>>>>> (where one has names like resource, RDF graph, IRI, and
>>>>>>>>>>>>> property).   Well, if rdf:Entity was not an IRI, then there might
>>>>>>>>>>>>> not be a conflation, but there would be other problems.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> peter
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>> On 12/22/2014 07:49 AM, Irene Polikoff wrote:
>>>>>>>>>>>>>> At some point in the discussion we have agreed not to talk about
>>>>>>>>>>>>>> resources when discussing RDF graphs and, instead, talk about
>>>>>>>>>>>>>> nodes.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I am talking about literal nodes.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Given the following triples
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> ex:house ex:number "2"^^xs:integer
>>>>>>>>>>>>>> ex:two rdf:type xsd:Integer
>>>>>>>>>>>>>> ex:house ex:number ex:two
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> There will be two different nodes for the number 2. The first
>>>>>>>>>>>>>> one
>>>>>>>>>>>>>> is the literal node. The second one is an IRI node. They will
>>>>>>>>>>>>>> never be the same and the graph represented by the first
>>>>>>>>>>>>>> triple is
>>>>>>>>>>>>>> not the same graph as the graph represented by the two last
>>>>>>>>>>>>>> triples.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The fact that ex:two may stand for the "real world" resource
>>>>>>>>>>>>>> that
>>>>>>>>>>>>>> philosophically is the same is irrelevant here as we are talking
>>>>>>>>>>>>>> about data structures and their processing.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The vocabulary term that is missing is the one that
>>>>>>>>>>>>>> identifies RDF
>>>>>>>>>>>>>> terms that can be subjects of a triple. In the context of this
>>>>>>>>>>>>>> working group, this is an important concept that needs its own
>>>>>>>>>>>>>> name. I propose rdf:Entity.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Irene
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Sent from my iPhone
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Dec 22, 2014, at 10:10 AM, "Peter F. Patel-Schneider"
>>>>>>>>>>>>>>> <pfpschneider@gmail.com> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> There are a number of intertwined issues here.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Are literal values resources in RDF? Yes, a literal value
>>>>>>>>>>>>>>> (e.g.,
>>>>>>>>>>>>>>> the number 2) is a resource.  This is just abiding by the
>>>>>>>>>>>>>>> principles of resources in the Semantic Web.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Can literal values have property values in RDF?  Yes, a literal
>>>>>>>>>>>>>>> value (e.g., the number 2) can have property values.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Can URIs denote literal values in RDF? Yes, a URI (e.g.,
>>>>>>>>>>>>>>> ex:two)
>>>>>>>>>>>>>>> can denote a literal value (e.g., the number 2).  This is just
>>>>>>>>>>>>>>> abiding by the principles of IRIs in the Semantic Web.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Is it possible in RDFS to make a URI to denote a literal value
>>>>>>>>>>>>>>> without causing a contradiction?  Yes, via something like
>>>>>>>>>>>>>>> ex:two
>>>>>>>>>>>>>>> rdf:type xsd:Integer.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Is it possible in RDFS to state that some literal value has a
>>>>>>>>>>>>>>> property value without causing a contradiction?  Yes, via
>>>>>>>>>>>>>>> something like ex:two rdf:type xsd:Integer. ex:two ex:prime
>>>>>>>>>>>>>>> xsd:true.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Is it possible in RDFS to directly state that a particular
>>>>>>>>>>>>>>> literal value has a property value?  No, because literals
>>>>>>>>>>>>>>> cannot
>>>>>>>>>>>>>>> be the subject of RDF triples.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Is it possible in RDF to get close to stating that a particular
>>>>>>>>>>>>>>> literal value has a property value? Yes, you can use
>>>>>>>>>>>>>>> reification
>>>>>>>>>>>>>>> as in  _:a rdf:subject 2. _:a rdf:predicate ex:prime. _:a
>>>>>>>>>>>>>>> rdf:object xsd:true.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> peter
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On 12/22/2014 06:39 AM, Irene Polikoff wrote:
>>>>>>>>>>>>>>>> RDF specification clearly says that there are 3 types of RDF
>>>>>>>>>>>>>>>> nodes: IRI, blank node and literal. Each has its own
>>>>>>>>>>>>>>>> unique/different characteristics including, for example, that
>>>>>>>>>>>>>>>> literal can only be an object of a triple and blank node can't
>>>>>>>>>>>>>>>> be a predicate of a triple.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I believe the specification makes it clear that these three
>>>>>>>>>>>>>>>> node types are disjoint. Thus, ex:two can not be a literal
>>>>>>>>>>>>>>>> node
>>>>>>>>>>>>>>>> as it is an IRI. I also thought we were discussing here RDF
>>>>>>>>>>>>>>>> nodes, not abstract concepts of literals.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I remember hearing that there were some discussions in the RDF
>>>>>>>>>>>>>>>> working group about letting literals be subjects, but this
>>>>>>>>>>>>>>>> proposal was rejected, wasn't it?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Irene
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Sent from my iPhone
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Dec 22, 2014, at 8:49 AM, "Peter F. Patel-Schneider"
>>>>>>>>>>>>>>>>> <pfpschneider@gmail.com> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On 12/22/2014 01:45 AM, ☮ elf Pavlik ☮ wrote:
>>>>>>>>>>>>>>>>>>> On 12/21/2014 01:38 AM, Peter F. Patel-Schneider wrote:
>>>>>>>>>>>>>>>>>>> In RDF all resources can have property values, even literal
>>>>>>>>>>>>>>>>>>> values.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> peter
>>>>>>>>>>>>>>>>>> Hi Peter :)
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Could you please explain it little more and if possible
>>>>>>>>>>>>>>>>>> share
>>>>>>>>>>>>>>>>>> links to
>>>>>>>>>>>>>>>>>> relevant references?
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks!
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The original version of RDF, as described in the RDF Model
>>>>>>>>>>>>>>>>> and
>>>>>>>>>>>>>>>>> Syntax Specification
>>>>>>>>>>>>>>>>> http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/, talks
>>>>>>>>>>>>>>>>> about
>>>>>>>>>>>>>>>>> Resources and Literals, but does not indicate directly
>>>>>>>>>>>>>>>>> whether
>>>>>>>>>>>>>>>>> they are disjoint.  However, there is already the idea that
>>>>>>>>>>>>>>>>> anything is a resource and that anything can described by a
>>>>>>>>>>>>>>>>> URI.  See Section 2
>>>>>>>>>>>>>>>>> http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/#basic and
>>>>>>>>>>>>>>>>> Section 5
>>>>>>>>>>>>>>>>> http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/#model for
>>>>>>>>>>>>>>>>> more information.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The original version of RDFS,
>>>>>>>>>>>>>>>>> http://www.w3.org/TR/1998/WD-rdf-schema/, which never
>>>>>>>>>>>>>>>>> became a
>>>>>>>>>>>>>>>>> full W3C recommendation, has the initial class hierarchy,
>>>>>>>>>>>>>>>>> including rdfs:Resource, rdfs:Literal, rdfs:Class, and
>>>>>>>>>>>>>>>>> rdf:Property in Figure 2.   In this figure, rdfs:Resource is
>>>>>>>>>>>>>>>>> the universal class, with rdfs:Class, rdf:Property, and
>>>>>>>>>>>>>>>>> rdfs:Literal all as subclasses. Here is the first direct
>>>>>>>>>>>>>>>>> requirement that literal values are resources.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The first formal treatment of RDF is in RDF Semantics
>>>>>>>>>>>>>>>>> http://www.w3.org/TR/2004/REC-rdf-mt-20040210/. Here
>>>>>>>>>>>>>>>>> interpretations for RDF are first defined, in Section 1.3
>>>>>>>>>>>>>>>>> http://www.w3.org/TR/2004/REC-rdf-mt-20040210/#interp,
>>>>>>>>>>>>>>>>> with the
>>>>>>>>>>>>>>>>> domain of an interpretation being the set of resources and a
>>>>>>>>>>>>>>>>> subset of the resources being literal values, as in the
>>>>>>>>>>>>>>>>> original version of RDFS. Properties are another subset
>>>>>>>>>>>>>>>>> of the
>>>>>>>>>>>>>>>>> resources, which are linked to their extent, which is a
>>>>>>>>>>>>>>>>> set of
>>>>>>>>>>>>>>>>> pairs over the resources.  There is no requirement here that
>>>>>>>>>>>>>>>>> literals cannot be the first element of a property pair.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> One might argue that the formal treatment is a misreading of
>>>>>>>>>>>>>>>>> the informal 1999 description of RDF, but the ability for
>>>>>>>>>>>>>>>>> literals to have property values has definitely been in RDF
>>>>>>>>>>>>>>>>> since at least 2004.  This stance is also consistent with the
>>>>>>>>>>>>>>>>> dictum that URIs can identify anything, which includes
>>>>>>>>>>>>>>>>> literal
>>>>>>>>>>>>>>>>> values.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> For example, one can say in RDF
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> ex:two rdf:type xsd:Integer .
>>>>>>>>>>>>>>>>> ex:two ex:prime xsd:true .
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Peter F. Patel-Schneider
>>>>>>>>>>>>>>>>> Nuance Communications
>>>>
>>>>
>
>
Received on Friday, 9 January 2015 02:41:18 UTC

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