Re: PIs

At 09:18 AM 9/12/96 GMT, Charles F. Goldfarb wrote:

>>If PIs are retained then PIC should be changed so that it is not > as this
>>is required for many processing instructions. (An alternative may be to
>>allow a character reference to be entered within a PI, but this would make
>>XML incompatible with SGML.)
>This is backwards. Changing PIC breaks SGML. A character reference would not be
>recognized by the SGML parser, but could be recognized by the XML application.

Nice to have you aboard, Charles.

I think on this one you're crediting us with too much subtlety.  References
aren't the issue - it's just that there are a lot of things that you'd like to 
put in PI's where it's irritating that you can't just use ">" to mean ">" - and 
since XML is almost certainly going to have a hardwired concrete syntax, why 
don't we change PIC to "%>" or "?>" or something, so as to make this irritation
go away?  Obviously the problem has no solution in the general case without
getting into some of the other mechanisms Charles mentions, but the
difficulties with the single character ">" are one of the many little things
that add up to constitute the barrier to entry to SGML.

Clearly this makes it harder to treat existing SGML documents with PI's as
XML... which raises an important point: we've been focusing on building 
XML to encourage a flood of *new* documents out of proprietary formats
into descriptive markup; should we be worried about supporting the existing
SGML legacy base?  I think not, but it's a valid question.

Cheers, Tim Bray
tbray@textuality.com http://www.textuality.com/ +1-604-488-1167

Received on Thursday, 12 September 1996 11:31:13 UTC