IPP>MOD: Problem in IPP encoding with "attributes-charset"

IPP>MOD: Problem in IPP encoding with "attributes-charset"

Ira Mcdonald x10962 imcdonal at eso.mc.xerox.com
Sun Mar 22 11:47:45 EST 1998


Hi Bob,


Yes, you're right that the charset and natural language attributes
must appear first.  That rule is near universal in modern protocols.


Cheers,
- Ira McDonald
  High North Inc
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Date: Fri, 20 Mar 1998 18:02:24 PST
To: ipp at pwg.org
From: Robert Herriot <robert.herriot at Eng.Sun.COM>
Subject: IPP>MOD: Problem in IPP encoding with "attributes-charset"
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I have found a problem that relates to the "attributes-charset" and 
"attributes-natural-language" attributes. 


They must be in the first group of attributes (the operation attributes), 
but they need not be first in the operation attributes group because the IPP 
model document states that attributes in groups such as "operation 
attributes" are unordered.  Except for this case, that is good. But the 
charset and natural language are special because they determine how name and 
text values of all attributes should be interpreted. Such a text or name 
attribute may precede the occurrence of "attributes-charset" and 
"attributes-natural-language". 


This makes an implementation more difficult because it cannot convert the 
octet string of the protocol to an internal String until it has found the 
"attributes-charset" value which could come many attributes later.


We need to change the documents to state that two attributes need to be 
first in the operations group, even though attributes in groups are 
otherwise unordered.  


How are you other implementors coping with this?


By the way, XML doesn't have this problem because the charset comes at a 
specific place at the very beginning and the language specification always 
precedes the text which it applies to.


Bob Herriot



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