Re: Closing on NIM requirements

[Jon Saperia <saperia@mediaone.net>]

on 04/16/2000 5:57 PM, Durham, David at david.durham@intel.com wrote:

> Actually, I think you can almost always find a mapping convention from some
> high-level modeling concept to any low-level implementation (Ie. Multiple
> inheritance to Single inheritance with associations simulating multiple
> inheritance). The point of the high-level model is that it should be easy to
> model your information with it... It is for the modeler who knows what the
> data needs to be but not how specific implementations work (or what their
> particular quirks may be). Using the conventions of the high-level model,
> standard mappings can be developed for specific implementations (ie. a
> high-level two-way association maps to an SNMP table entry with a successor
> + predecessor row pointer). Standard mappings will hopefully make the
> translation automatic.
> 
> Besides being most convenient to the modeler, the high-level model must be
> maximally expressive, allow the modeler to specify constraints, etc. such
> that the resulting model is unambiguous (and, thus, so are the mappings).
> 
> Basically, we need a simple way to get the information out of the expert's
> heads and into a high-level model (once), then derive the low-level models
> from that root model.
> 
> -Dave
I think you have said very well what you mean here. My observation has been
that for efficiency, the details of the implementation approach 'bleed
through' to the model, and often appropriately so.  Please do not take this
a criticism of the effort, just that my experience has shown me that the
technology and the model often inform each other for best results.

The best example I can give is of different database technologies. Even at
this fairly specific level, common generic interfaces suffer from
performance limitations that direct interfaces do not suffer from. I am a
fan of layering and using different levels of abstraction, but they must be
used carefully or we will end up with a solution that looks better on paper
than in the network.

/jon