element order error processing

[Andy Bierman <ietf@andybierman.com>]

Hi,

I am confused as to which error-tag to use for wrong element order.

For example:

Given a simple data model:

element foo {
  element a,
  element b,
  element c
}

The use of missing-element vs. unknown-element error-tag is confusing:

Given this PDU fragment:

 <foo>
    <a/>
    <c/>
 </foo>

It is clear that a 'missing-element' error for "/foo/b" should
be generated here.

What about this?:

 <foo>
    <a/>
    <c/>
    <b/>
 </foo>

A reasonable implementation choice would lead one to generate
a 'missing-element' error for "/foo/b" when "/foo/c" is encountered.
But "b" isn't missing, it is in the wrong place.  The only other
error choice seems to be  'unknown-element' for "/foo/b" in
this case, which is totally confusing because "b" is not unknown
at all.  Generating a 'missing-element' and 'unknown-element' for "b"
in the same <rpc-reply> is even worse.

What should the correct error response be in this case?

Is an agent implementation allowed to ignore wrong-order errors
or must all elements always be given in a fixed order?  This seems
like a CLR to me.


thanks,
Andy


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