Re: Non-deterministic content model

[Francis Norton <francis@redrice.com>]

Robin Cover wrote:
> 
> On Thu, 14 Jun 2001, Marcus Carr wrote:
> 
> >
> > Sam Willmott from OmniMark released a white paper on content model algebra
> > in the early nineties. He concluded that there was only one content model
> > that cannot be disambiguated and I have yet to see proof to the contrary.
> > The model is:
> >
> >    (x, (y, x)*, y?)
> >

I'm trying to iterpret this interesting theory thread in the light of
existing validation technologies.

Taking the chess moves interpretation, the ambigous model above can be
implemented in Schematron as:

<sch:schema xmlns:sch="http://www.ascc.net/xml/schematron">
	<sch:title>chess</sch:title>
	<sch:pattern name="game">
		<sch:rule context="game">
			<sch:assert test="*[1][self::white]"
			>The game must start with a white move.</sch:assert>
			<sch:assert test="count(*) = count(white) + count(black)"
			>The game may contain only black and white moves.</sch:assert>
		</sch:rule>
		<sch:rule context="white">
			<sch:assert test="not(preceding::*[1][self::white]"
			>White moves must alternate with black moves.</sch:assert>
		</sch:rule>
		<sch:rule context="black">
			<sch:assert test="not(preceding::*[1][self::black]"
			>Black moves must alternate with white moves.</sch:assert>
		</sch:rule>
	</sch:pattern>
</sch:schema>

Is it equally simple to implement this ambiguous model in other schema
technologies?

Francis.