Subject: RE: Note on Rev

From: "Dagostino, Tom" <[email-masked]>
Date: Fri, 6 Jul 2001 13:35:28 -0700

What is the backward compatibility problem.  If this applies to Ver 3.3 or later files what is the issue?

Tom Dagostino
Modeling Manager
Mentor Graphics Corp.
SAE
[email-masked]
503-685-1613

-----Original Message-----
From: Al Davis [mailto:[email-masked]]
Sent: Friday, July 06, 2001 11:53 AM
To: Scott McMorrow; Peters, Stephen
Cc: [email-masked]; ibis
Subject: Re: Note on Rev

On Friday 06 July 2001 09:55 am, Scott McMorrow wrote:
> Stephen,
>
> I have the following suggestions to eliminate this problem:
>
> 1) Require that keywords do not appear in any text blocks.  Where a
> keyword is defined to include the [keyword] syntax.  This would be
> an unusual circumstance anyway.  It is highly unlikely that in
> production models that a [keyword] would appear in a text block
> sections.  These sorts of things generally only occur in examples
> and can be easily removed.
>
> 2) Require an [End Block] keyword for all sections with text
> blocks.
>
>
> The requirement that keywords begin in column 1 seems more onerous
> to me than either of these suggestions.  I would "really" like to
> be able to use indented structure within all future models to
> facilitate better understandability.  Also, I would really like to
> not have to deal with a stupid parser that spits out my files when
> somehow I managed to create a model that does not position a
> keyword in column 1.

We discussed this, both in connector and IBIS-X.  The problem is 
backward compatibility.  

Under suggestion #1, this basically prohibits any use of "[" in a 
text block.  This was the original intended way of doing it.  In 
testing, I found that there were too many old files being rejected.

Suggestion #2 is the obviously superior method, except that there are 
lots of files that don't have the end marker, and we want to maintain 
100% backward compatibility.

Still, this does not require that EVERY keyword begin in column 1.  
The restriction could only apply to those terminating a text block, 
or the text block could be terminated by a line containing a "[" as 
the first non-whitespace character, following a blank line.

---

From: Al Davis <[email-masked]>
Date: Fri, 6 Jul 2001 14:15:21 -0700

> 3.3 or later files what is the issue?

Here are a few reasons:

1. Some of the old tools will be used to generate new style models, 
by first generating the old style model, then adding the one new 
feature.  They would then need to bring the whole file into 
compliance.

2. Some simulators will be using the new technology (macro language 
based) software to process even the oldest files.  Probably all tools 
newly adding IBIS support will be in this category.  Some of the old 
tools will switch to the new method even for the old files because of 
lower maintenance costs.  For this reason, the new software must 
accomodate the old files.  This is a basic principle in the design of 
the macro language.  This one is easily solved by a "compatibility 
mode" in the software, that accepts the implied block ends.

3. It is my opinion that the new work should concentrate on what does 
not work well in the old standard.  I have not heard many complaints 
about the header section.  It is also my opinion that we should not 
make gratuitous changes.

Having said that, some of the "decisions" were based on what we 
thought public opinion would be.  Now that we have some comments from 
outside the committee, it really is arbitrary and could go either way.