Re: which class of programming languages, XML Schema language belongs

HTML+CSS is Turing complete, known for more than 11 years:

https://lemire.me/blog/2011/03/08/breaking-news-htmlcss-is-turing-complete/#:~:text=A%20programming%20language%20is%20Turing,%2C%20C%2C%20and%20so%20on
.


Thanks,
Dimitre

On Fri, Mar 11, 2022 at 6:22 AM Marcus Reichardt <[email protected]> wrote:

> It's not entirely clear CSS isn't Turing-complete yet though, or bound to
> become Turing-complete soon.
>
> Not talking about that old "proof" where the user has to perform clicks to
> function as tape, but rather about newer CSS features such as var() in
> combination with grid and other constraint-based layouts etc. which I'd not
> be surprised to hear having become accidentally Turing-complete considering
> the grab bag CSS has amounted to.
>
> Apart from that, how about XSD is a regular tree grammar? Though with
> unconstrained XPath assertions or XPath 2+ existential quantifiers etc. XSD
> might eventually end up becoming Turing-complete, too.
>
> FWIW, it has long been established that XSD is undecidable ie. the problem
> of answering whether an arbitrary XSD can have a valid instance isn't
> decidable in general due to interaction of key constraints with
> minOccurs/maxOccurs as I recall, even without XPath assertions.
>
> Best,
> Marcus Reichardt
> sgml.io
>
>
> > Am 11.03.2022 um 13:29 schrieb Pete Cordell <[email protected]
> >:
> >
> > On 11/03/2022 08:48, Michael Kay wrote:
> >> Well, I would say that XSD is indeed a "formal computer language", but
> not a "programming language"; I don't think you can describe something as a
> programming language unless it is Turing-complete.
> >> I don't know of any universally accepted categorisation scheme for
> formal computer languages, and without such a scheme you can't say where a
> particular language fits; but it's certainly reasonable to describe XSD as
> a constraint specification language or as a data definition language (if
> indeed those two categories are distinct).
> >
> > A related perma-topic is "Is HTML a programming language?"
> >
> > I'm in the "No, because it is not Turing-complete" camp (for example, it
> has no conditionals) but it does instruct a computer to do things and so
> others say it is.
> >
> > I'd say if "programming language" was a spectrum, HTML would be more of
> a programming language than XSD.
> >
> > To add more confusion, for most programming languages such as C++ and
> Java, it's very specific what the language tells the computer to do.
> >
> > With XSD, the XSD can be used in many ways by a computer.  Does that
> suggest it is "something else"?
> >
> > Pete.
> > --
> > ---------------------------------------------------------------------
> > Pete Cordell
> > Codalogic Ltd
> > Read & write XML in C++, http://www.xml2cpp.com
> > ---------------------------------------------------------------------
> >
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-- 
Cheers,
Dimitre Novatchev
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