Subject: Re: Using SGI's IRIS Explorer in Computational Chemistry

From: JEREMY WALTON <[email-masked]>
Date: 31 Mar 94 11:18:00 WET

>> 	I would suggest that AVS and its Molecule Data Type are much better
>> for chemistry, since the data type was an integral part of the initial 
>> design of AVS.  It is very flexible and as such there are many ways in which
>> data can be stored in its various components, which are hierarchical lists.
>> I have a nine+ page description of how the MDT is structured if anyone is
>> interested (at least, how it is structured and used in the Chemistry Viewer).
>> In general, the MDT is an organized collection of atom-based substructure
>> and quantum chemical information.

Hi Doug,

My copy of the "AVS Technical Overview" shows the Molecule Data Type being 
added to AVS as a new feature at version 3 in March 1991.  By contrast, the 
molecular pyramid datatype was a feature of version 1.0 of IRIS Explorer,
announced the same year.  However, this is really of little relevance to this 
group (I'm sure we don't want an AVS vs IRIS Explorer discussion along the 
lines of the recent FORTRAN vs C flame wars ;-) ).  

One problem that some users have had with the pyramid datatype is its
complexity - partly because it was designed so that the same heirarchical
structure can be  used to store both  molecular data and unstructured grids. 
However, once mastered, the molecular pyramid can indeed be used powerfully -
e.g. the EyeChem suite of chemistry modules developed by Omer Casher and his
colleagues, which are part of version 2.2 of IRIS Explorer.  Malcolm and I
have been having (somewhat fitful) exchanges on ways in which this can be
improved, possibly by making use of IRIS Explorer's functionality for creating
user-defined types.  Either way, it'd be nice to hear more about the AVS MDT,
so if there was any more information which could be shared with the group, I'm
sure I'm not the only one who'd be interested.

Cheers,

Jeremy

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|  Jeremy Walton                                   [email-masked]     |
|  The Numerical Algorithms Group Ltd, Oxford, UK  [email-masked]           |
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