[Crm-sig] Issue: Solution for Dualism of E41 Appellation and rdfs:label

Martin Doerr martin at ics.forth.gr
Wed Sep 12 16:55:21 EEST 2018


Dear Richard,

I basically agree with your comments. Specifically however, I indeed 
wanted to say that the official definition of rdfs:label makes it 
exactly a subproperty of P1 (or shortcut of it) in any correct use of 
RDFS. If we want to mix RDFS models, we should have an opinion about 
their compatibility. Otherwise, we would have to regard them as 
alternative that cannot be compared with the CRM.

I am not happy with adding rdfs:label to instances of Appellation, 
because this would mean it is a name for a name and not the name. I 
would sympathize with George using rdfs:value, if it had the respective 
semantics.

What we need, to my opinion, is a property of Symbolic Object we may 
call it "has symbolic content" or "has symbolic content inline" or 
anything better, which defines that the symbolic content *is identical 
to* the Literal, *abstracted *to the "level of symbolic specificity" 
that the Literal implies and that conforms to the identity condition of 
the Symbolic Object, i.e., characters of a certain script, or whatever. 
That would make the meaning of the "value" unambiguous.

We may need add another property, such as "is contained in" or so 
pointing to a URL actually holding an instance of its content, again 
abstracted to the "level of symbolic specificity" that the file instance 
implies and that conforms to the identity condition of the Symbolic Object.

Whereas the shortcut interpretation is attractive, it is not exactly the 
same. Using a shortcut, we say that the intermediate node is of 
different, independent nature from the terminal node. Here, we do not 
say "Appellation" is related to something called "Literal". We say "this 
Appellation IS itself what is in this Literal". That may or may not be a 
reason to reject this interpretation.

We also have to distinguish Appellations and other Symbolic Objects 
which have multiple symbolic forms, i.e. spelling variants, versions 
etc., from those *being one* symbolic form. The rdfs:value has no means 
to express that. I believe we need yet another property "has symbolic 
content variant". In that case, the URI is necessary, to my opinion.

I think the polymorphism we describe here, well studied in 
object-oriented languages, is in the nature of Appellations. The problem 
for me is, that the the respective KR models have NOT THOUGHT of the 
case that such polymorphisms can occurr. Nevertheless, RDFS is tolerant 
enough to accept the Superproperty statement, but not to create a class 
which is either URI or *inline expanded* object.

This polymorphism occurs EXCLUSIVELY for Symbolic Objects with symbol 
sets a certain machine supports. Another reason not to use rdfs:value, 
because it does not give credit to the fact that only Symbolic Objects 
can have such a "value".

I agree that we may over-think the point. As I mentioned, the 
superproperty statement I propose has no other effect than that I can 
get E41's and labels back by querying P1 only.

Opinions?

Best,

Martin

On 9/12/2018 9:56 AM, Richard Light wrote:
>
> On 11/09/2018 20:02, Martin Doerr wrote:
>> Dear All,
>>
>> Firstly, apologies, the RDF was wrong, it was intended to be P1 is 
>> superproperty of rdfs:label.
> I'm not sure that this is something we need to state at all, and I 
> worry that - if it is included in our RDFS Schema - it may bring 
> unwanted side-effects.  Isn't this saying that any instance of 
> rdfs:label is to be treated as an instance of P1?  Bear in mind that 
> CRM data may co-exist in triple stores in company with other RDF data, 
> which may well use rdfs:label for its own purposes. This assertion 
> that 'all rdfs:labels are P1 relationships' would then be applied to 
> this other data as well.  This might well result in incorrect/spurious 
> results when SPARQL queries are applied to the data.
>
> In general, I suggest that we are ok to define sub-classes/properties 
> of standard RDFS types, but we shouldn't define 
> super-classes/properties of them.  (I would welcome comments on the 
> validity of this suggestion from someone who understands RDF better 
> than me.)
>
>> Semantically, the range of rdfs:label, when used, is ontologically an 
>> Appellation in the sense of the CRM.
> Agreed (see my reply from yesterday).  The conclusion I draw from this 
> is that we can validly say:
>
> E1 rdfs:label "string value" is a shortcut for the path 'E1 CRM 
> Entity' 'P1 is identified by' 'E41 Appellation' ...
>
> in exactly the same spirit as the similarly-worded note which we find 
> in the definition of P1 itself. (Obviously, by using this shortcut, we 
> lose the information that this string value is an Appellation, but 
> that's the nature of short-cuts.)
>
>> I agree with George, that all RDF nodes should have a human readable 
>> label. They name the thing, even if it is a technical node.
>> I would find it confusing to say, labels are not to be queried, only 
>> to be read, and the "real" names must have a URI,
>> regardless weather I have more to say about it.
>>
>> I am really not a fan of punning, we definitely forbid it in the CRM.
>>
>> The point with Appellations is that some, the simple ones, can 
>> directly be represented in the machine, or be outside. The solution 
>> to assign a URI in all cases, and then a value or label, does not 
>> make the world easier. It is extremely bad performance. We talk here 
>> about implementation, not about ontology.
>> You get simply a useless explosion of the graph for a purpose of 
>> theoretic purity.
> Agreed. What we need to do is to propose a simple way of expressing 
> simple Appellations in RDF.  That is why my shortcut definition above 
> ends with '...': I don't think we have yet decided how to do this.
>
> I've just been looking over the draft document we are trying to write, 
> and it currently says that a fully-worked-out path will use 'P3 has 
> note -> E62 string' to express the value of an E41 Appellation.  This 
> (i.e. the suggestion to use P3) comes from the definition of the 
> superclass E90 Symbolic Object.  A comment in our draft RDF document 
> questions whether this is sufficiently precise, since P3 is simply "a 
> container for all informal descriptions about an object that have not 
> been expressed in terms of CRM constructs".  I suggest that we need 
> either to use rdfs:value to hold the string value, or (better) to 
> define a CRM-specific subproperty of rdfs:value and use that.  (This 
> subproperty could be part of the published CRM, or it could just form 
> part of the 'RDF implementation' guidelines.)  I don't think that we 
> should use rdfs:label here.
>
> I don't think we should concern ourselves with URLs in our RDF 
> guidance document.  Any implementer of our RDF solutions can choose to 
> assign a URL to represent any node in the structure, but it won't 
> change the logic of the resulting RDF, or how it responds to SPARQL 
> queries.
>
>>
>> Those claiming confusing should be more precise. Has someone looked 
>> at query benchmarks? Has someone looked at graphical representations 
>> of RDF graphs. Do they really look better?
>>
>> So either we either ignore the issue, and write queries that collect 
>> names either via P1, URI and a value/label, or via a label, because 
>> this is where names appear in RDF, we make no punning, but our 
>> queries implement exactly this meaning. So, we are not better, but do 
>> as if we wouldn't know.
>>
>> Or, we describe the fact by punning, have one superproperty for all 
>> cases, which we can query, and stop thereby the discussion if labels 
>> are allowed or not, and how they relate to appellations. The punning 
>> comes in, because the range of the superproperty must comprise the 
>> ranges of the subproperties. We can play a bit more, make the punning 
>> with a superproperty of P1, and have both P1 and rdfs:label 
>> subproperties of it, if this is preferred.
>> The solution I describe is just a logical representation of the 
>> situation, not creating a different situation. It just says that 
>> names can be complex objects or simple literals.
> As I said yesterday, I don't see how any punning strategy can make 
> differently-structured RDF equivalent for the purposes of querying. 
> Therefore, I think we will have to accept that if we allow more than 
> one way of representing a given statement in CRM RDF, we will have to 
> construct queries which look explicitly for each of the possible patterns.
>
>> The problem is, that the RDF literals do have meaning beyond being 
>> symbol sequences.
> Insofar as they have such meaning, I would argue that we define it 
> (i.e. that meaning) by the CRM context in which we place the 
> string/literal value.  I think there is a danger that we could 
> over-think this problem.
>
> Richard
>>
>> The punning does not introduce the problem. With or without, the 
>> queries have to cope with names in either form.
>> This holds similarly for space primitives and large geometry files, 
>> for short texts and equivalent files etc.
>>
>> Opinions?
>>
>> Best
>>
>> Martin
>>
>>
>
> -- 
> *Richard Light*
>
>
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  Dr. Martin Doerr              |  Vox:+30(2810)391625        |
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                                |  Email: martin at ics.forth.gr |
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