Re: Blank nodes must DIE! [ was Re: Blank nodes semantics - existential variables?]

Antoine,

> physical quantities are not the same as measurements
Nicely put!
Similar to names are not the same as people, perhaps?

And à propos uncertainty.
I am guessing that uncertainty of measurement could well be expressed using an appropriate ontology with UCUM (and possibly other literal types) as the underlying physical quantities.
As https://www.w3.org/TR/swbp-xsch-datatypes/#sec-numerics says:
> The second issue concerning precision of measurements, must be addressed at the modelling level by using objects to state precision or error properties for measurements. This is not a bad approach, in any case, since there are often other properties or metadata associated with a measurement.


I think I will need to adjust how I view literals! - Oh dear.
(Do not adjust your mind, the fault is in reality? :-) )

But I would like the developers' world of tooling to stay as simple as it currently is.
Which to me means anyone wanting one of these magic literals of any kind to be used in RDF, to provide not only the description for the literal, but also define how those literals should be represented in RDF.
And also, not just have SPARQL support in their favourite SPARQL store, but also the open source code to do the conversion, and even a service to do it, hopefully at an endpoint that is an aggregate of all these different literals.

In that sense, such things are ontologies that also have a literal representation/serialisation, it seems to me.
That fact that it has come via the literal spec is no longer important.

> On 24 Jul 2020, at 20:34, Antoine Zimmermann <antoine.zimmermann@emse.fr> wrote:
> 
> Hugh,
> 
> 
> Le 24/07/2020 à 20:53, Hugh Glaser a écrit :
>> Thanks, all very helpful.
>> I just have one disagreement, which is not necessarily important to your argument (sorry!), but I don't want to let through without comment.
>>> On 24 Jul 2020, at 19:23, Antoine Zimmermann <antoine.zimmermann@emse.fr> wrote:
>>> 
>>> <snip>
>>> It truly is the spirit of RDF datatypes to have to parse the lexical form to understand what a literal means.
>>> <snip>
>>> --AZ
>> I really don't agree with this, and this may be where some trouble arises.
>> The "spirit of RDF" to me says that the whole point of literals is that is where meaning bottoms out - if you want meaning, it goes in the RDF.
>> Viewing literals as having structured meaning is what gets people into the trouble of equating names with people, etc..
>> And indeed that a literal could be "10 inches" instead of "10".
>> I see that what is being proposed around UCUM as very interesting, and moving away from that spirit, but personally I think it is wrong to say that there is no change being proposed.
>> At an extreme, this would mean having RDF graphs with a single triple that has a huge and complex N3 document in its single literal, with a full RDF semantics.
> 
> It's good that you mention this because there has not been any argument about why put something in a literal and why not. It is obvious that putting everything in a literal, as an rdf:Turtle datatype or something like that, seems completely silly.
> 
> What literals should be used for is to convey information about something that can be represented exactly in digital form. So, for example, if I want to tell you about the date 24th July 2020, in Central Europe Summer Time, I can represent it exactly as an xsd:date. The digital information tells you *exactly* what I'm talking about. However, if I want to tell you something about France, I cannot give you a digital representation of Antoine Zimmermann. It's always going to be partial, imperfect, and for sure not referring to the physical entity that consists of my body and mind. A physical quantity like the speed of light can be conveyed exactly, perfectly, in digital form. If I write:
> 
> "‎299792458 m/s" is exactly what I'm talking about. There is no missing information.
> 
> Now, there is some caveat that needs to be expressed: physical quantities are not the same as measurements. If I want to say what the length of my table in my living room, I cannot convey this information exactly. I cannot say that it is exactly "2.5 m". However, I can say that my measurement, however imprecise it is, gives a measure of "2.5 m", which is an exact physical quantity. I still need some extra information to specify the precision:
> 
> <measurement> :value "2.5 m"^^cdt:ucum;
> :precision "1 %"^^cdt:ucum .
> 
> Moving things out of a graph into a literal does not mean that RDF loses its power and that you need not express relations between entities with identifiers, predicates, and all that.
> 
> --AZ
> 
>> Where does it stop?
> 

-- 
Hugh
023 8061 5652

Received on Saturday, 25 July 2020 12:41:29 UTC