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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
same.
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
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