Subject: Re: New Notification Log MIB Draft

From: David Perkins <[email-masked]>
Date: Thu, 5 Nov 98 10:28:23 pst

HI,

We on the SMIv2 team really did have much discussions on this topic. The latest
draft of the SMI document contains an example showing a read-only column with
a DEFVAL clause specified. I think that the example is not a strong one for
showing usage of a DEFVAL on a non create-read column. Are there any 
strongly compelling examples in existing MIB modules of a DEFVAL on a
non create-read object. If so, please send me private Email with
a reference and I'll summarize.

Let me provide one example of use of the DEFVAL clause on a scalar object.
Consider the two objects for a simple thermostat. The first
is the desired temperature, thermDesiredTemp, and the second one is
the actual temperature, termActualTemp.

It many MIB designers for these two objects would say that a DEFVAL is
appropriate for object termDesiredTemp with, say, a value of 70 degrees F.
Is this a compelling example?

On Thu, 5 Nov 1998 15:47:24 +0100  Juergen Schoenwaelder wrote:
>
>>>>>> Martin Bjorklund writes:
>
>Martin> Right.  But the latest draft from the SMIv2 team also says
>Martin> that:
>
>: Note that with this definition of the DEFVAL clause, it is appropriate    |
>: to use it for any columnar object of a read-create table.  It is also     |
>: permitted to use it for scalar objects dynamically created by an agent,   |
>: or for columnar objects of a read-write table dynamically created by an
>: agent.
>
>Martin> How should this be interpreted?  In our agent implementation,
>Martin> *all* objects can be viewed as being dynamically created,
>Martin> because MIBs are loaded into the agent during run-time.  Since
>Martin> such an implementation always is feasible, all scalars could
>Martin> have a DEFVAL clause, couldn't they?
>
>The main purpose of the DEFVAL clause at the time it was invented was
>to define the value for columnar objects during row creation when no
>explicit value was provided during row creation. Enough people argue
>now that the usage of DEFVAL is also handy for scalars that are
>dynamically created and the text in the new draft reflects this view
>of the community. 
>
>(Note that this usage of DEFVAL serves a different purpose and has
>implications especially on agent toolkits. However, this issue has
>been discussed at some length at the SMI BOF in Chicago - the SMI-DT
>just tried to document the concensus in Chicago.)
>
>Keith and I still believe that there is an important conceptual
>difference between columnar objects that are designed to be
>dynamically created and scalar objects that are typically created
>during (sub)agent startup. But we do not think that this issue is
>important enough to start lengthy discussions and to hold of the SMIv2
>from progressing to full standard. The agent toolkit vendors at the
>SMIv2 BOF did agree to the new interpretation and this is probably
>the most important voice in this issue.
>							Juergen
>-- 
>Juergen Schoenwaelder  [email-masked] http://www.cs.tu-bs.de/~schoenw
>Technical University Braunschweig, Dept. Operating Systems & Computer Networks
>Bueltenweg 74/75, 38106 Braunschweig, Germany.        (Tel. +49 531 / 391 3289)
>

/[email-masked], David T. Perkins
Date: 11/05/98, Time: 10:28:23

---

From: Bob Natale <[email-masked]>
Date: Fri, 06 Nov 1998 17:17:09 -0500

>At 11/5/98 10:28 AM, David Perkins wrote:

Hi Dave,

>Are there any strongly compelling examples in existing MIB
>modules of a DEFVAL on a non create-read object.

Yes...gains (perhaps modest) in:

	- documentation clarity
	- state definition
	- engineering discipline

...at (virtually) no additional cost, with no
appreciable negative side-effects.

Cordially,

BobN
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