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RE: Can XML documents have loops (cycles)?

• From: "Costello, Roger L." <costello@mitre.org>
• To: "xml-dev@lists.xml.org" <xml-dev@lists.xml.org>
• Date: Mon, 10 Oct 2011 12:28:40 +0000

Thanks David.

So would it be accurate to say that: 

1. XML documents may have loops (cycles).

2. XML parsers just report the loops; XML parsers do not traverse them.

/Roger

-----Original Message-----
From: David Carlisle [mailto:davidc@nag.co.uk] 
Sent: Monday, October 10, 2011 8:21 AM
To: Costello, Roger L.
Cc: xml-dev@lists.xml.org
Subject: Re:  Can XML documents have loops (cycles)?

On 10/10/2011 13:03, Costello, Roger L. wrote:
> Why doesn't an XML parser have to worry about falling into an
> infinite loop?

because an xml parser never follows ID/IDREF links, it just reports
them. You only have to worry about looping if you are traversing the
implied graph. An XML application using the results of a parse may need
to worry about that, but the parser doesn't. You may go through many
stages of application before any application need worry, for example
your file may be parsed without error, may be transformed to html with
(say) xslt without error, with the links being turned into html
hypertext links. Loops in that link structure are not errors either and
cause no problem for an html browser. However, if you have a set of
trained monkeys (or a search engine web crawler) that is mechanically
traversing the generated html links then _they_ (or it) need to worry
about loops. but that is a long way removed from the original XML file.

David

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• Follow-Ups:
  • Re: Can XML documents have loops (cycles)?
    • From: David Carlisle <davidc@nag.co.uk>
  • Re: Can XML documents have loops (cycles)?
    • From: Chris Burdess <dog@bluezoo.org>

• References:
  • Can XML documents have loops (cycles)?
    • From: "Costello, Roger L." <costello@mitre.org>
  • Re: Can XML documents have loops (cycles)?
    • From: David Carlisle <davidc@nag.co.uk>