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RE: SGML queries

• To: 'John Cowan' <jcowan@r...>, xml-dev@l...
• Subject: RE: SGML queries
• From: "Bullard, Claude L (Len)" <clbullar@i...>
• Date: Tue, 10 Sep 2002 15:56:43 -0500

*Bonehead elements* might be good.  Other than in 
the SGML Handbook, I've never seen these used 
in practice. The reason is that even where as 
the handbook says, the SGML produces no errors, the 
author may not get the right effect because the 
rules for doing this right require an intimate 
knowledge of the contexts.   The SGML Handbook (C.F. 
Goldfarb) takes up this subject in Annex C.1.2.1.

Assuming that your SGML Declaration has "OMITTAG YES" 
and you aren't playing with short tags.

"A start tag is omissible when the element type is 
contextually required and any other elemnt types that 
could occur are contextually optional." pg 74

"Even when an element is contextually required, its 
start tag cannot be omitted if the element type has 
required attributes or a declared content, or if the 
instance of the element is empty."  pg 75

Section 4.6.1 takes up the OMITTAG feature in more 
detail.  If you don't have a copy of the handbook, 
let me know and I will transcribe the relevant 
page or two.

"Although the basic principles of start tag 
ommission are reasonably straightforward, the 
detailed requirements and definitions are highly 
technical.  They hinge on the concepts "contextually 
optional element" and "contextually required element". p 163

Ugly stuff.

len

-----Original Message-----
From: John Cowan [mailto:jcowan@r...]
Sent: Tuesday, September 10, 2002 3:05 PM
To: xml-dev@l...
Subject:  SGML queries


1) What is the correct jargon for an element which allows both start-tag and
end-tag omission?  I have been calling them "phantom elements", since they
may be ESIS-present but lexically absent.

2) I note that when SP has a choice between inferring a missing end-tag and
inferring a missing start-tag (and phantom element), it infers the end-tag:

<!DOCTYPE root [
        <!ELEMENT root - - (foo, foo?)>
        <!ELEMENT foo - O (#PCDATA | bar)*>
        <!ELEMENT bar O O (foo)>
        ]>
<root> <foo> case 1 <foo> case 2 </root>

does not generate an ESIS containing "bar", and even adding a "</bar>"
before "</root>" does not help.  Is this behavior prescribed by the
Standard?

-- 
De plichten van een docent zijn divers,         John Cowan
die van het gehoor ook.                         jcowan@r...
      --Edsger Dijkstra                         http://www.ccil.org/~cowan

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