OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.


Help: OASIS Mailing Lists Help | MarkMail Help



   Re: [xml-dev] RE : [xml-dev] Comparison of Xml documents

[ Lists Home | Date Index | Thread Index ]

Bob Wyman wrote:
 > Bob Foster wrote:
 >>The naive approach to determining equivalence between two documents
 >>would be to define a recursive procedure that normalizes and
 >>collects element contents into sequences or sets, as appropriate,
 >>then compares the result for equality.
 > 	I think what you really want to do here is convert the XML to
 > "canonical form."

I really don't. Canonical form is another textual representation, extra 
overhead and an unwanted level of indirection (the comparison should 
report the result of the comparison in terms of the original text).

But rather than respond to the rest of your note point by point, let me 
say I was disappointed that, since you know much more about ASN.1 than I 
do, you didn't respond to my main point.

I didn't forget ASN.1 as a schema language, I know about SET and 
SEQUENCE from your earlier posts, but I don't know what they mean, in 
the following sense.

Ordering is both a lexical and a semantic constraint. For the purposes 
of comparison, there are three possibilities: order may be lexically 
required; order may be lexically insignificant but semantically 
significant (like the dots and dashes in Morse code); or order may be 
both lexically and semantically insignificant (like the items in a 
shopping list).

Only in the latter case would I want a comparison to report that two 
sequences that differed from each other only in order were, in fact, the 

In ASN.1, does SET mean that order is both lexically and semantically 
insignificant (as it does in mathematics)?

Or, is ASN.1 SET the same in this respect as '&' and 'all' in the other 
schema languages? Does it simply mean that order is lexically 
insigificant with no comment on semantics, because the latter aren't 
required for validation?

Finally, if SET does mean that order is lexically and semantically 
insignificant, how does one specify in ASN.1 that order is lexically 
insignificant but semantically significant?

Bob Foster


News | XML in Industry | Calendar | XML Registry
Marketplace | Resources | MyXML.org | Sponsors | Privacy Statement

Copyright 2001 XML.org. This site is hosted by OASIS