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

From: Robert Herriot <[email-masked]>
Date: Fri, 20 Mar 1998 18:02:24 -0800

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

---

From: "Turner, Randy" <[email-masked]>
Date: Sat, 21 Mar 1998 15:19:16 -0800

I believe we have found some other hidden dependencies that are similar
to this, but we just reorder the logic of our attribute processing in
order to "do the right thing". While doing in this in the protocol
specification may help some implementations, it hasn't hindered our
efforts too much. But then again our server is only a proof-of-concept
implementation with limited capability. But even with our prototype,
taking the attributes in a particular order hasn't been too difficult.
If the WG agrees to make this change to the documents, I would have no
problem with it.

Randy
	-----Original Message-----
	From:	Robert Herriot [SMTP:[email-masked]]
	Sent:	Friday, March 20, 1998 6:02 PM
	To:	[email-masked]
	Subject:	IPP>MOD: Problem in IPP encoding with
"attributes-charset"

	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

	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.  

	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

---

From: [email-masked] (Ira Mcdonald x10962)
Date: Sun, 22 Mar 1998 08:47:45 PST

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
----------------------------------------------------------------------
>From [email-masked] Fri Mar 20 21:15:39 1998
Date: Fri, 20 Mar 1998 18:02:24 PST
To: [email-masked]
From: Robert Herriot <[email-masked]>
Subject: IPP>MOD: Problem in IPP encoding with "attributes-charset"
Sender: [email-masked]
Status: R

Bob Herriot