A different comment syntax question

Rob Cameron (cameron@cs.sfu.ca)
Fri, 17 Jul 1998 08:53:55 -0700 (PDT)

Although the XML specification makes clear that "--" is not allowed
in comments, there is another case that is less clear. Can the
body of a comment end in a single hyphen, that is, is a comment like
"<--A+, A or A--->" legal? There is no explicit mention of this
in the text of the specification, but a careful read of the grammar
does not allow it.

Comment ::= '<!--' ((Char - '-') | ('-' (Char - '-')))* '-->'

Clarification of this issue is important to designers of XML
generation tools in particular. If you need to generate an
XML comment from an arbitrary string do you have to deal with
both the double hyphen case and the trailing hyphen case?

If, as I assume, the answer is that only the double hyphen case
is a concern, then the grammar needs to be changed.

Comment ::= '<!--' (Char* - (Char* '--' Char*)) '-->'

Robert D. Cameron, Associate Professor cameron@cs.sfu.ca
School of Computing Science FAX: (604) 291-3045
Simon Fraser University
Burnaby, B.C., Canada V5A 1S6

Internet Electronic Library Project at SFU
http://elib.cs.sfu.ca/