Subject: Re: Protocol: modification items may violate schema

From: "Jim Sermersheim" <[email-masked]>
Date: Fri, 05 Sep 2003 15:59:39 -0600

Let me pose some silliness and wonder at how to deal with it.
 
An attribute called X is of syntax integer
 
A modify adds the value "1#qrs#5" to X, then deletes the value
"1#xyz#5" from X
 
The server tries to evaluate the two values being updated on X. Neither
of them are integers, thus it can't use its normal compare routines to
check for equality. I suppose the server could (in the event of syntax
violations) fail over to using an exact octet match.
 
While the server is gathering up these modifications (in order to later
commit them), I guess it can't hold the attribute values in a
syntax-based data structure, because it can't rely on the values
adhering to the syntax.
 
I think there's something even more ugly, but I can't think of it
now...
 
Jim

>>> Timothy Hahn <[email-masked]> 9/5/03 1:25:28 PM >>>

Jim, 

I had always interepreted this as indicating that even if "silly
things" are done in some of the modificationItems, that the server
shouldn't necessarily fail the modification because an "intermediate
result" was not compliant to the schema definitions. 

Re-stated, an entry in the process of being modified (within an atomic
operation) is allowed to be non-compliant to the schema, but by the end
of applying all the modifications (at the end of the atomic operation)
the entry MUST be schema compliant. 

That's how I always interpreted it. 

Regards,
Tim Hahn

Internet: [email-masked]
Internal: Timothy Hahn/Durham/IBM@IBMUS
phone: 919.224.1565     tie-line: 8/687.1565
fax: 919.224.2540

"Jim Sermersheim" <[email-masked]> 
Sent by: [email-masked] 
09/05/2003 02:45 PM         
        To:        <[email-masked]> 
        cc:        "Duane Buss" <[email-masked]>, "Vithalprasad
Gaitonde" <[email-masked]>, "Joseph Cook" <[email-masked]>,
"Jim Schnitter" <[email-masked]>, "Mike Cronquist"
<[email-masked]>, "Richard Ellis" <[email-masked]>, "Steve
McLain" <[email-masked]>, "Parameswaran S" <[email-masked]>,
"Susan Perrin" <[email-masked]> 
        Subject:        Protocol: modification items may violate
schema

All,

An issue has been raised regarding the language in 4.6:

"While individual modifications may violate the directory schema, the
resulting entry after the entire list of modifications is performed
MUST
conform to the requirements of the directory schema."

While I believe most server implementors understand this to mean that
while any one modification item may cause an object class violation,
the
entire set of modifications must be evaluated an no error returned if
the net effect would not violate schema.

For example, in one test it is expected that given the entry
(singleValAttr is a SINGLE-VALUE attribute):

dn: dc=example
objectclass: x
singleValAttr: val1

the following modify should not error:
dn: dc=example
changetype: modify
add: singleValAttr
singleValAttr: val2
-
delete: singleValAttr
singleValAttr: val1

While it's obvious that the net effect is to have a single value
(val2)
in singleValAttr, because the order is backward, a server doesn't like
it.

Other examples might include:
- Deleting a distinguished name value and re-adding the same value
- Adding an attribute value of invalid syntax and then removing it.
- Adding a value that would produce contraintViolation, then removing
it.

Regarding the statement above: I've always read this as a requirement
on the data being presented to the server--that at least the resulting
entry MUST conform. I haven't (until recently) thought about it as a
requirement that the server allow silly things to be present in a list
of modification items.

What do others feel? Is there a need for clarity here? Are these kinds
of tests valid indicators of standards-compliance?

Jim

---

From: "Howard Chu" <[email-masked]>
Date: Fri, 5 Sep 2003 16:09:52 -0700

-----Original Message-----
  From: [email-masked]
[mailto:[email-masked]]On Behalf Of Jim Sermersheim
  Sent: Friday, September 05, 2003 3:00 PM
  To: [email-masked]
  Subject: Re: Protocol: modification items may violate schema

  A modify adds the value "1#qrs#5" to X, then deletes the value "1#xyz#5"
from X

  The server tries to evaluate the two values being updated on X. Neither of
them are integers, thus it can't use its normal compare routines to check for
equality. I suppose the server could (in the event of syntax violations) fail
over to using an exact octet match.

  While the server is gathering up these modifications (in order to later
commit them), I guess it can't hold the attribute values in a syntax-based
data structure, because it can't rely on the values adhering to the syntax.

  I think there's something even more ugly, but I can't think of it now...

  Jim

  Jim,

  I had always interepreted this as indicating that even if "silly things"
are done in some of the modificationItems, that the server shouldn't
necessarily fail the modification because an "intermediate result" was not
compliant to the schema definitions.

  Re-stated, an entry in the process of being modified (within an atomic
operation) is allowed to be non-compliant to the schema, but by the end of
applying all the modifications (at the end of the atomic operation) the entry
MUST be schema compliant.

  Regards,
  Tim Hahn

                To:        <[email-masked]>
                cc:        "Duane Buss" <[email-masked]>, "Vithalprasad
Gaitonde" <[email-masked]>, "Joseph Cook" <[email-masked]>, "Jim
Schnitter" <[email-masked]>, "Mike Cronquist" <[email-masked]>,
"Richard Ellis" <[email-masked]>, "Steve McLain" <[email-masked]>,
"Parameswaran S" <[email-masked]>, "Susan Perrin" <[email-masked]>
                Subject:        Protocol: modification items may violate
schema

  All,

  "While indi! vidual modifications may violate the directory schema, the
  resulting entry after the entire list of modifications is performed MUST
  conform to the requirements of the directory schema."

  While I believe most server implementors understand this to mean that
  while any one modification item may cause an object class violation, the
  entire set of modifications must be evaluated an no error returned if
  the net effect would not violate schema.

  dn: dc=example
  objectclass: x
  singleValAttr: val1

  While it's obvious that the net effect is to have a single value (val2)
  in singleValAttr, because the order is backward, a server doesn't like
  it.
  !
  Other examples might include:
  - Deleting a distinguishe! d name v alue and re-adding the same value
  - Adding an attribute value of invalid syntax and then removing it.
  - Adding a value that would produce contraintViolation, then removing
  it.

  Jim

I'm surprised this discussion is still going on. X.511 is pretty clear on
this - the result must conform, but it is necessary to allow intermediate
steps to violate the schema

On the other hand, Jim's example with the bogus values for Add/Delete of an
Integer attribute should fail immediately due to Syntax violation. The point
is that temporary ObjectClass violations are allowed, so long as the final
object conforms to the requirements of its ObjectClass, but other violations
return errors immediately.

Also, from one of Jim's other examples: removing an attribute or value that
is part of the entry's RDN is explicitly not allowed.

   -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support