REPLY Open Source Simulation Software (SD6800)

[SDMAIL Malczynski, Leonard A]

Posted by  "Malczynski, Leonard A" <lamalcz at sandia.gov>

Greetings,
 
Everyone should be aware of Jim Hines' 'SMILE' effort to develop a 
common model format.
There is a description of an XMILE format proposed by Vedat Diker and 
others.
Karim Chichakly also has published on this.
(see the sds-isig group at 
http://tech.groups.yahoo.com/group/sds_isig/ if you are interested)
 
I submitted a paper in Nijmegen, using what I learned from Kim Warren, 
about why SMILE or XMILE will not be realized. Basically, software firms 
are competing for our business as Richard Dudley mentioned.
 
Maintaing the basic stock and flow paradigm is a must for them to be 
methodologically consistent. If we take a look beyond that, the programs 
are quite different.  Each has implemented modeling features that cannot 
be easily translated, e.g. conveyors in Stella; some might even require 
'programming', e.g. allocate functions in Vensim and Studio; and very 
different IDEs (Interactive Development Environments). If there is a 
common, easily translated format, low switching costs may put one or 
more of these firms out of business. I have been very interested in the 
SD tool market and have seen some convergence or 'follow the leader' 
behavior by the firms in terms of feature additions.
 
The competitive strategy of a firm may be producing niche products for 
the broad system dynamics community.
 
When I say broad, the scope ranges from academic exercises to very large 
models with too much historical data (ususally prompted by clients who 
are still not convinced of the power of the methodology) to flight 
simulators that are very interface intensive and error trapping to 
models that incorporate other paradigms e.g. operations research.
 
The firms have to make a decision. They have limited resources with 
which to construct their SD software. They must allocate those resources 
to stay in business. Should they allocate to developing a common format 
or add new features to their tool?
 
Pedagocially, a simple open source product would be useful. Although as 
Richard Stevenson stated, the vendors provide free or low cost crippled 
versions of their products, sufficient for learning SD principles 
(perhaps these students would then use these tools t work once gainfully 
imployed?). A 'free' open source tool would not satisfy some of the 
other users I mentioned above. Their motivations might not be pure SD 
but they have found client niches that benefit from the SD methodology 
and applications that have become what I call 'extra methodological'.
 
Jean-Jaques point about models from the conference papers has been 
bothering me too. I admit to having presented work based on one product 
that cannot be duplicated at all or without much difficulty in other 
products.  At the risk of being lambasted, relatively simple models 
could be presented in all 3 major formats if the authors have access and 
facility with all 3 products. Again, another barrier.
 
Regards,
Len Malczynski
Posted by  "Malczynski, Leonard A" <lamalcz at sandia.gov>
posting date  Sun, 9 Mar 2008 10:36:15 -0600