Re: [xml-dev] What is a sematic data model?

At 2021-11-12 16:10 +0000, Hans-Juergen Rennau wrote:
>"You create a semantic data model for a problem 
>domain (for example, in UML), and then you 
>define XML or JSON representations of the data 
>in that domain. The conceptual data model comes 
>first, the concrete realisations come second." Michael Kay
>
>This sounds to straightforward, intuitive, 
>compelling - that it puzzles me why it seems to 
>be done only very rarely, and concerning the 
>approach how to do it there does not seem to be 
>any established good practice. The OASIS work 
>Ken points to looks exactly like a step in that 
>direction, but probably very few people are aware of it?

I wish more people were aware of what we have been doing.

The UBL project turned 20 years old last month. 
We've been using CCTS for modeling and our NDRs 
(an OASIS innovation) since soon after the 
project inception, though the NDRs have evolved a 
lot over the years. The JSON clauses in the NDRs 
are a quite recent addition to the XML clauses.

The use of github for non-technical committee 
members to generate XSD and JSON-schema 
constraint expressions is new in version 2.3. The 
sources are fully exposed in the repository (I'm 
not using my obfuscation techniques).

Going from CCTS to XSD and, separately, from CCTS 
to JSON-schema means we aren't trying to convert 
our XSD expressions directly into JSON-schema 
expressions. Perhaps they can be, but it is 
irrelevant. What is relevant is these each are 
mechanical expressions of the single CCTS model.

The CCTS 2.01 model for business documents comes 
from the United Nations Centre for Trade 
Facilitation UN/CEFACT. The lowest XSD fragment 
in the UBL schema tree is a copyrighted UN/CEFACT 
file of component types. There is no such 
fragment for JSON-schema so I write one.

As there is no mixed content in CCTS, I found it 
straightforward to create NDRs for producing a 
JSON-schema expression of the content 
constraints. And documents conforming to the 
schemas can be transliterated losslessly between XML and JSON and back again.

I would entertain proselytizing our 
accomplishments in this regard as a presentation 
to any interested conference audience either 
remotely or, if the conference can help with 
travel, on-site. I'm anxious to get on the road 
again, but my OASIS work is entirely unfunded.

. . . . . . . . Ken

p.s. I haven't copied here the links that I posted originally earlier:

http://lists.xml.org/archives/xml-dev/202111/msg00031.html

>And would RDF not be a top candidate for the 
>semantic models on which to build API definitions, but who does it?
>
>The apparent lack of interest (?) in that 
>straightforward (?) approach is above all 
>puzzling if one considers how data integration - 
>API integration - becomes an increasingly 
>pressing problem. So bridging between different 
>syntax is probably only a minor application, the 
>main one being bridging between different 
>message types. There must be a reason for this 
>contradiction, and I would like to understand it.
>
>Hans-Jürgen
>
>Am Freitag, 12. November 2021, 14:11:32 MEZ hat 
>Michael Kay <> Folgendes geschrieben:
>
>
> >
> > Michael, what is a "semantic data model"?
>
>A semantic data model tells you how the items in 
>your data relate to things in the real world. An 
>XML document might have a <product> element, but 
>it doesn't tell you what a product is - and it's 
>always more complicated than you think (for 
>example, if you put your cornflakes in a 
>Christmas-themed package one week, does that make it a different product?).
>
> > Would you give an example of a semantic data 
> model for XML and an example of a semantic data model for JSON, please?
>
>You're putting the cart before the horse. You 
>create a semantic data model for a problem 
>domain (for example, in UML), and then you 
>define XML or JSON representations of the data 
>in that domain. The conceptual data model comes 
>first, the concrete realisations come second.
>
>Of course, people often skimp on data modelling 
>and can get into a mess as a result. I did some 
>modelling work with a TV company that couldn't 
>agree what a "channel" was - some people thought 
>it was a content service that people subscribed 
>to, others that it was a set of electrical 
>signals transmitted on a particular frequency.
>
>
> > How are their semantic data models used to 
> transform XML to JSON and vice versa?
> >
>
>You design an XML representation of the data 
>model, and you design a JSON representation of 
>the data model, and then you work out how they 
>relate to each other, by referring back to the data model.
>
>Michael Kay
>Saxonica


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