I believe that this more general approach needs to be explicitly stated.
I had assumed that when the spec talks about “letters” (or strings) it refers 
to “Unicode letters”. Therefore a normalization step would always be needed 
before string comparison.
Searching the spec, I see no relevant reference to Unicode.

Side note: I can easily envision a license identifier with Greek letters (the 
Greek-ported CCs, for example), although probably not in the pre-defined short 
identifiers list.

-- zvr

From: [email protected] 
[mailto:[email protected]] On Behalf Of Wheeler, David A
Sent: Friday, November 13, 2015 10:45 PM
To: Ben Balter <[email protected]>; Gary O'Neall <[email protected]>; 
[email protected]
Subject: RE: Are SPDX license identifiers case-sensitive?

My personal preference would be that the license identifiers be *matched* by 
forcing everything to lower case, AND that SPDX encourage *displays* of a 
license identifier to use the exact mixed-case as shown in the SPDX lists.  The 
mixed-case forms use normal English conventions (all-caps for acronyms, initial 
caps for proper names), and it’s NICE to have a display that uses standard 
conventions.  However, requiring exact-case matching is a recipe for subtle 
mistakes; the actual matching should be case-insensitive, just like license 
expressions which use them are.

I note that the OSI website accepts both the exact-case and the all-lower-case 
versions of the SPDX license IDs. That’s why I say “to lower case” instead of 
“match ignoring case” – in the case of URLs, you have to know EXACTLY what to 
transform it to before you can get matching ignoring case.  (I realize that in 
Greek there are 2 lower case s’s, but there are no license id’s with Greek 
letters and there IS a way to deal with that anyway, so that’s not relevant.)

The “licensee” gem could reply with a new “SPDX” field that returned the 
mixed-case string value, while doing lookups on all lower case.

--- David A. Wheeler

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