Re: [Json] Proposed minimal change for strings

[Paul Hoffman <[e-mail]>]

<no hat>

On Jul 2, 2013, at 8:44 PM, Nico Williams <[e-mail]> wrote:

> Huh?  Do you mean that any code unit may be allowed if escaped?  

That is exactly what the current document says, I believe. Do you see anything in the grammar that says differently?

>> In section 1 (Introduction):
>>  Change the sentence about Unicode characters to:
>>    A string is a sequence of zero or more Unicode code units [UNICODE].
> 
> These aren't Unicode things though.  

Yes, they are. See the Unicode Standard, definition D77. Do you see anything in the Unicode Standard that disagrees with D77?

>> In section 2.2 (Strings):
>>  Leave the production for "unescaped" as-is.
>> In section 3 (Encoding):
>>  Add "Some strings, notably those that have unescaped surrogate code units
>>  (value 0xD800 to 0xDFFF), cannot be encoded in UTF-8."
> 
> Unescaped and *unpaired*.

No, any surrogate code point. RFC 3629, the IETF's definition of UTF-8, says:
   The definition of UTF-8 prohibits encoding character numbers between
   U+D800 and U+DFFF, which are reserved for use with the UTF-16
   encoding form (as surrogate pairs) and do not directly represent
   characters.
Similar language is used in The Unicode Standard's definition of UTF-8 (D92), and of UTF-32 (D90).

--Paul Hoffman