Marc.McDonald@Design-Intelligence.com wrote:
> 
>         > XML requires deterministic content models. This allows
>         > validators to do their job without having to look more
>	  > than one element ahead
>         > or do brute force tree searches.
> 
> The validator may not have to look more than 1 element ahead, but it does
> need to look <n> elements behind or construct a tree representation for the
> pattern due to optional elements:
> 
> <!ELEMENT x (a? | b?)>
> <!ELEMENT a (c,d,e,f,g)>
> <!ELEMENT b (c,d,e,f,h)>
> 
> With an input of elements c, d, e, f, h in element x.

Actually, the content model for "x" is in error there, so any
XML processor is allowed to report an error however rudely it
chooses to do so.  That content model is "ambigious".

- Dave

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