case in Selectors API


I note that we have another example of case-mapping woes in the 
Selectors API document. This case disturbs me and I think we should 
submit a comment. The document is:

The text in question is:

Note: The case sensitivity of namespace prefixes is effectively 
determined by the implementation of the NSResolver object that is used 
to resolve the namespaces.

Note: In Unicode, caseless matching requires both strings that are being 
compared, to be case folded prior to performing a binary comparison 
[CaseMap]. However, since case folding is not the same as simply 
uppercasing or lowercasing both strings and because the comparison is 
being performed by the NSResolver object implemented by the author, this 
specification cannot require case insensitive namespace prefixes.

My problems with this text are:

1. It seems to me that the WebAPI is doing implementers a disservice 
here. If they would otherwise have required case-insensitivity except 
for the requirement that implementers of NSResolver understand Unicode 
case folding, then ignorance of Unicode case folding shouldn't be a 
barrier to requiring case-insensitivity. I see no reason why a Spec 
cannot require something if it is both well-documented and necessary, 
which appears to be the case here.

For that matter, it isn't strictly a "Unicode" problem (as implied by 
the above): it is a general problem of case-normalizing text. Namespace 
prefixes are not limited to ASCII, and implementations of Selectors API 
need to deal with that fact.

2. Case-insensitive mapping is not completely sufficient anyway. No 
mention is made of normalization. If there is something they are not 
going to require but should mention, it would be Unicode normalization 
(see CharMod-Norm). Binary comparison of Unicode strings for character 
equivalence requires this normalization over-and-above case-folding.



Addison Phillips
Globalization Architect -- Yahoo! Inc.
Chair -- W3C Internationalization Core WG

Internationalization is an architecture.
It is not a feature.

Received on Thursday, 7 February 2008 16:29:39 UTC