Thanks for the thoughtful responses to my original posting.
In fact, it was not my intention to spark a discussion on the pros and cons of a an SD markup language, whether vendors would want to invest in developing one, etc. Instead, my original question assumed that there is a group of people out there who are interested in discussing the development of such a language (rather than whether there should be one), and I was asking where that discussion could be hosted.
I asked the question (rather than just starting a forum somewhere else) because I do feel that this forum would be the ideal place to host it, especially given Bob's floating of that idea in his words which I quoted. But it seems that this feeling is not shared by members of this forum, indicating that the right course of action is for those of us (assuming it's not just me...) who want to discuss the practicalities to go off somewhere else.
This creates a bit of a problem for me personally, because (sorry, don't know how to express this better) I am not really a System Dynamics person. Rather, I am an ecological modeller who has developed software (Simile) which happens to have an SD capability. This is to a large extent a difference of culture - there is a lot of overlap between "ecological models" and "System Dynamics model" - but none-the-less real for all that. However, I have for many years found it odd that the SD community has not moved towards a common model-representation language (or rather, has not turned the on-off discussions over this time into a community endeavour). Hence my setting up of the XMILE wiki during a previous iteration, to try to help things along. And I would again be happy now to join in with a community initiative to work through these issues.
I'd like to make three further points:
First, I would really encourage anyone interested in this discussion to check out SBML - the Systems Biology Markup Language (http://sbml.org/Main_Page
). Systems Biology, which is largely concerned with the modelling of biological pathways, emerged a long time after SD - indeed (some time after the first mention of an SD interchange language...). But quite soon the community (largely the developers of similar-but-slightly-different software tools) got together and designed a common data model and an XML realisation. Significantly, this has spawned the development of over 200 (!) software tools capable of reading and writing SBML- almost exactly reflecting Travis's thinking in the most recent posting in this thread. Also significantly, the BioModels web database now holds some 820 models expressed in SBML, along with web tools for viewing and simulating these models, and generating code in various languages (again reflecting Travis's ideas).
Sure, there are differences between the two fields, but there are also significant similarities. For example, the reaction concept which underpins SBML is also a cosmetic overlay on top of a set of ODEs, just like SD; and some of the SBML-compliant tools are commercial. So I don't think we should dismiss the SBML experience outright.
Second, and again reflecting Travis's posting, I think that it is better to think in terms of a declarative model representation language rather than a model interchange language. Once we have an open, standard, XML-based language, then all sorts of things will flow from that. Anyone can develop an XSLT transform (for example) which can display/process an SDML model in some novel way, and put it on the web - totally changing the culture away from the exchange of models between "the big three". For an example of what I have in mind, please look at http://www.itfutures.ed.ac.uk/robert_muetzelfeldt_synopsis.htm
and the associated presentation.
Third, we are starting to see the emergence of various new kids on the block when it comes to SD software, including web-based ones. Maybe not individually, but collectively these are game-changers. Being typically free-to-use and small, the inclination to buy into a common language is much greater.