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RE: Non-deterministic content model

• From: Derek Denny-Brown <derekdb@m...>
• To: Murali Mani <mani@C...>, "K.Kawaguchi" <kohsukekawaguchi@y...>
• Date: Wed, 13 Jun 2001 14:04:00 -0700

> Also I think, the language specified by ((a, b)*, a) cannot 
> be written as
> an 1-unambiguous regular expression or 1-unambiguous model group -- I
> think --

(a, (b,a)*)

It is not an 1-unambiguous model group (I think), but it is an
1-unambiguous regular expression (I'm sure).

Orignal RegExp -> NDFA 
0	a:1 a:2
1	b:0
2	$

DFA
0' (0)	a:1'
1' (1,2)	b:1' $


Derek Denny-Brown



> -----Original Message-----
> From: Murali Mani [mailto:mani@C...]
> Sent: Wednesday, June 13, 2001 1:36 PM
> To: K.Kawaguchi
> Cc: Derek Denny-Brown; Steve Rosenberry; xml-dev@l...
> Subject: Re: Non-deterministic content model
> 
> 
> 
> Actually Kohsuke is right -- (a & b?) is *not* inherently 1-ambiguous.
> 
> Also I think, the language specified by ((a, b)*, a) cannot 
> be written as
> an 1-unambiguous regular expression or 1-unambiguous model group -- I
> think --
> 
> when you see an "a" in the string, you do *not* know whether it is the
> first a or the second a, unless you know whether there is b following
> it.
> 
> i think the above example holds for all model groups defined 
> to date --
> thanks a lot.
> 
> are there any opinions/suggestions??
> 
> Derek, try to give the content model for ((a, b)*, a), if you are not
> convinced.
> 
> thanks and regards - murali.
> 
> On Wed, 13 Jun 2001, K.Kawaguchi wrote:
> 
> >
> > > (a, b? | b?, a)
> >
> > Since the above is the equivalent of ( a | ab | ba ),
> > you can write it as
> >
> > (a,b?) | (b,a)
> >
> > which is deterministic.
> >
> > How about this?
> >
> > > (a b)* a?
> >
> >
> > I think this cannot be written by the deterministic content model.
> >
> > regards,
> > ----------------------
> > K.Kawaguchi
> > E-Mail: kohsukekawaguchi@y...
> >
> >
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> 

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