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   RE: [xml-dev] schema-aware XML parser (java heap error)

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Thank you Michael.

Unfortunately, large number of measurement parameter values are the nature
of the PCM airborne encoders. My customer obviously needs to validate his
XML data with my XSD externally before feeding it into my application.  I
was trying to save him the extra step.    I am assuming that XML file size
would not be an issue since I am using an event-driven parser!


> -----Original Message-----
> From: Michael Kay [mailto:mike@saxonica.com]
> Sent: Thursday, June 02, 2005 3:29 PM
> To: Farid.Mahini@L-3com.com; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] schema-aware XML parser (java heap error)
> > My java app. which uses the standard schema-aware XML parse 
> > (packaged with
> > j2sdk1.5.0-01) was hanging up and sometimes I got a java heap 
> > error msg.   I
> > narrowed it to the maxOccurs attribute of a complexType 
> element  in my
> > schema. It seems if maxOccurs> 2000 for this element, the 
> app fails.  
> > 
> The standard algorithms for generating a finite-state machine 
> from a grammar
> suffer from the problem that the number of possible states 
> becomes very
> large when you use a large value of minOccurs or maxOccurs, 
> which causes an
> increasing use of memory. Saxon's schema processor deals with this by
> treating a large maxOccurs as if you had specified "unbounded" (with a
> warning), which is only marginally better than falling over 
> completely.
> Henry Thompson was promising to publish an improved algorithm 
> but I haven't
> seen it yet...
> I would suggest that you treat this constraint as one of 
> those that are best
> checked at application level, or using a tool such as schematron.
> Grammar-based validators aren't good at this job.
> Michael Kay
> http://www.saxonica.com/


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