Re: [Diffserv] Comments on the TCB of the Conceptual Model - msg 1 of 2

[Brian E Carpenter <[e-mail]>]

Andrea,

Thanks for the clarifications. In turn let me repeat for the Nth time
that the diffserv conceptual model is not intended to be and never
claimed to be a formal information or OO model with mathematical
conformance requirements. 

  Brian

Andrea Westerinen wrote:
> 
> To jump in this thread, since PolTerm definitions are referenced (I love
> spontaneous publicity :-) ....
> 
> I would like to be clear that PolTerm is defining "information model" and
> "data model".  Here are the current terms:
> $ information model
> An abstraction and representation of the entities in a managed environment,
> their properties, attributes and operations, and the way that they relate to
> each other. It is independent of any specific repository, application,
> protocol, or platform.
> $ data model
> A mapping of the contents of an information model into a form that is
> specific to a particular type of data store or repository.  A "data model"
> is basically the rendering of an information model according to a specific
> set of mechanisms for representing, organizing, storing and handling data.
> It has three parts [DecSupp]:
> -       A collection of data structures such as lists, tables, relations, etc.
> -       A collection of operations that can be applied to the structures such as
> retrieval, update, summation, etc.
> -       A collection of integrity rules that define the legal states (set of
> values) or changes of state (operations on values).
> (See also "information model.")
> 
> We are not defining "model" since that is a very overloaded term and not
> directly applicable to policy.
> 
> I would agree with John that the "Conceptual Model" is not an "information
> model" in that it does not detail specific properties, associations, etc.
> It does discuss concepts - of which a TCB is a concept.  However, since TCB
> was not previously modeled (until MIB -04, I am told), one might ask whether
> it is a "good" concept.  But that is a different question.  Typically, in OO
> design, your nouns (concepts) equate to classes.
> 
> WRT "efficiency" and "info models", I would say that these terms are
> related.  "Efficiency" implies fewer/more intuitive classes and properties,
> rather than "processing efficiency".  The point about TrafficClass as an
> "index" is related to TrafficClass as a valid property in an info model,
> conveying a certain labeling/indexing semantic - not an "index" into an
> "info model".  It seems that a property is more "efficient" than a new class
> representing a TCB, to which other classes must be associated.
> 
> WRT "implementation" and "data models", as seen in the definition above, a
> data model does dictate an implementation (i.e., a data store).  If there
> are standards around this (for example, LDAP schema), then the
> implementation is defined.  If not (sadly), people are free to do things
> their own way, but should/must maintain the semantics of the information
> model.
> 
> Andrea
> 
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]On Behalf
> Of Andrew Smith
> Sent: Thursday, July 13, 2000 10:06 AM
> To: John Strassner
> Cc: [e-mail]; Fred Baker
> Subject: Re: [Diffserv] Comments on the TCB of the Conceptual Model -
> msg 1 of 2
> 
> 1. I don't see how "efficiency" can be applied to an "information model" (by
> your definition). These don't, by definition, have indices.
> 
> 3. OK - by "implementation" I thought you were talking about "this is how to
> implement a router" kinds of things. So I think you are talking about
> "implementation of a data model": in that case, yes, it is supposed to guide
> you in how to do that. What's wrong with that? How else are you going to
> implement data models? Is everyone else going to do it their own way?
> 
> Andrew
> 
> John Strassner wrote:
> >
> > Comments inline.
> >
> > regards,
> > John
> > ----- Original Message -----
> > From: "Andrew Smith" <[e-mail]>
> > To: "John Strassner" <[e-mail]>
> > Cc: <[e-mail]>; "Fred Baker" <[e-mail]>
> > Sent: Thursday, July 13, 2000 12:31 AM
> > Subject: Re: [Diffserv] Comments on the TCB of the
> > Conceptual Model - msg 1 of 2
> >
> > > John,
> > >
> > > 1. You mentioned "efficiency" in your message sent
> > Thursday, July 06, 2000 10:58
> > > AM (enclosed). I guess you meant efficieny of words typed
> > or characters in the
> > > draft or something.
> >
> > Thanks for finding this. The full quote was:
> >
> > "Again, a key point to note is that we defined a single
> > attribute as the index that you are looking for, instead of
> > having to use the entire concept of the TCB. This worked
> > better, and was much more efficient."
> >
> > So efficiency here doesn't have to do with how easily
> > characters are typed; rather, it meant that the use of the
> > TrafficClass attribute was a more efficient way of defining
> > the index that you were looking for instead of trying to use
> > the entire concept of the TCB, which doesn't have such an
> > index. If that really is at the risk of being confused with
> > how easily characters can be typed please let me know and
> > I'll rewrite my comments. ;-(
> >
> > > 2. I loook forward to seeing Andrea's definition of
> > "model".
> > >
> > > 3. I am struggling to find where in the -03 model draft
> > you think implies that
> > > it is an implementation guide - please clarify. If there
> > is nowhere then I guess
> > > that removes your main concern with the draft.
> >
> > I've stated this several times, here is (again) the primary
> > quote that worries me (from the abstract):
> >
> > "This model serves as the rationale for the design of an
> > SNMP MIB [DSMIB] and for other configuration interfaces
> > (e.g.  [DSPIB]): these should all be based upon and
> > consistent with this model."
> >
> > If phrases like "...serves as the rationale for the
> > design..." and "...based upon and consistent with this
> > model" is not a guide to implementation, what do they mean?
> > Again, I would be happy if you simply deleted this entire
> > sentence.
> >
> > > Meanwhile, an updated draft has to be submitted - I hope
> > it will address some of
> > > your concerns but I'm not optimistic that it will solve
> > all.
> > >
> > > Andrew
> > >
> > >
> 
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