REPLY Open Source Simulation Software for SD (SD6813)

[SDMAIL Magne Myrtveit]

Posted by  "Magne Myrtveit" <magne at myrtveit.com>


Bobby  Powers writes:
> How about the following as a start?  Different languages that 
> additional information to accompany the equations
> of variables can add additional elements to <var>.  Also since type is 
> just a string, you can include additional
> variable types without changing the save file specification.  Also, 
> newer versions of the specification can be
> implemented and versioned by changing the markup attribute.

Dear Booby,
 
Thanks for your response.
 
To create an XML specification that can store the structure of a model 
is not be too hard. The example you enclosed in your posting shows how 
this can be achieved.
 
In order for one software to load a file created by another software, 
the *semandics* of each equation must be understood and converted. (The 
conversion is sometimes trivial, and sometimes virtually impossible).
 
As part of my reasearch (my wife keeps asking me when I will finish my 
PhD:-) I have devloped two meta languages for storing models. One uses 
XML, which is good for automatic storage, exchange, and translation of 
models. The other is a plain text format, which is easy to read for 
humans. (Typical use: Model equations appendix of book or paper).
 
I created the formats for two reasons:
1) To learn about the different modelling langauges.
2) To have a format that I could use for my own product (Smia).

The proposed formats have the advantage that they already have all (?) 
the features needed to store complete models stored by the most recent 
version of:
 
o) Powersim Studio
o) Vensim
o) Microsoft Excel (yes, that's right)
o) Dynaplan Smia
 
Stella/iThink should be quite easy to add to the list, if someone has a 
way to output their models as text.
 
If someone is interested in looking at the formats for a third use 
(conversion), I'd be glad to share them with you.
 
Best regards,
Magne Myrtveit
Posted by  "Magne Myrtveit" <magne at myrtveit.com>
posting date  Wed, 12 Mar 2008 13:11:59 +0100