Re: questions on XML sgml decl's charsets
I strongly suspect that most SGML declarations include
"SHUNCHAR CONTROLS etc." only because few people ever
write an SGML declaration from scratch; most just copy
an existing one and modify it, leaving the parts they don't
understand untouched. Since few people understand SHUNCHAR
(I am not among them, BTW), that clause has survived largely
unmutated from the ancestral declaration in ISO 8879.
I'm guilty as charged.
Let me ask the converse question: is there a rationale
*for* specifiying shunned characters?
It makes your editor go BEEP when you try to insert Ctrl-Foo, and your
parser spew out a line complaining bitterly, thus preventing people
inserting unwanted bytes by accident or design. But I'm sure there's
more to it than that.