Re: [Json] JSON: remove gap between Ecma-404 and IETF draft

[[e-mail] (Henry S. Thompson)]

John Cowan writes:

> Joe Hildebrand (jhildebr) scripsit:
>
>> If 404 doesn't allow [a BOM], I don't see a strong need to add it.
>> Parsers can always be more forgiving of what they will parse than what
>> the spec says, particularly since section 9 says "A JSON parser MAY
>> accept non-JSON forms or extensions".
>
> It's not clear that 404 disallows it, since 404 is defined in terms of
> characters, and a BOM is not a character but an out-of-band signal.

I think this is a crucial observation.  I note that XML approaches
this problem in what might be a useful way.  The XML ABNF makes no
mention of BOM, it's not part of any XML document as such.  But it
_is_ allowed.  The relevant wording [1] is:

  Entities ... may begin with the Byte Order Mark described by Annex H
  of [ISO/IEC 10646:2000], section 16.8 of [Unicode] (the ZERO WIDTH
  NO-BREAK SPACE character, #xFEFF). _This is an encoding signature,_
  _not part of either the markup or the character data of the XML_
  _document._ XML processors must be able to use this character to
  differentiate between UTF-8 and UTF-16 encoded documents. [emphasis
  added]

ht

[1] http://www.w3.org/TR/REC-xml/#charencoding
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       Henry S. Thompson, School of Informatics, University of Edinburgh
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