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There is a reasonably long history of work on dynamic networks, and a 
couple of choices of free public software now available as well.

Two you should consider are Tom Snijder's StOCNET/Sienna packages, and the 
new "statnet" package from the UW network modeling group.  Snijder's 
package uses a windows menu driven interface, so is very easy to work 
with.  "statnet" uses the stat package R as an interface, so is works on 
all platforms.  it's also more flexible and capable of handling larger 
networks, but there is a steeper learning curve if you're not already 
familiar with R.

Both come up first in a google search now, so are easy to find.

best,
Martina Morris



On Thu, 20 Jul 2006, David Krackhardt wrote:

> *****  To join INSNA, visit http://www.insna.org  *****
>
> Roy (and Chai Choon-Lee),
>
> Interesting alternative.  I've been a fan of the systems dynamics models for 
> years.  But, I am reminded of two things.  First, the most robust general 
> finding of the systems dynamics literature is that it is the structure (the 
> existence of feedback loops), not the flows or rates, that make a substantial 
> difference in the behavior of the model.  This is where SNA can shine.  SD 
> assumes a structure and simulates a result.  SNA can actually explain 
> (predict) the structure, leading to insights into why the critical feedback 
> loops exist (perhaps stochastically).  It can also lead more efficiently to 
> insights about critical nodes (centrality, structural holes, etc.) as a 
> function of the structure.
>
> This, however, does not take away from your primary point: SNA more often 
> than not deals with fixed stationary, not dynamic, models.  Which brings me 
> to my second thought: Some networkers have combined both the structural 
> orientation of SNA and the dynamic orientation of simulations.  Foremost 
> among these is Kathleen Carley, in my view.  She has several large scale 
> packages that are built around and calculate network concepts but also use 
> agent modeling techniques to simulate dynamics.  One advantage to her work is 
> that she permits the structure itself to be dynamic, depending on the rules 
> that govern the formation and dissolution of network links.  I would 
> recommend considering some of her packages in addition to the MIT-based SD 
> software.  You can find out more about these at her CASOS website; or, since 
> she produces stuff so fast I am not sure the website can keep up, perhaps you 
> are better off asking her directly ([log in to unmask]).
>
> -David
>
>
>
> --On Thursday, July 20, 2006 9:11 AM +0100 Roy Greenhalgh <[log in to unmask]> 
> wrote:
>
>> *****  To join INSNA, visit http://www.insna.org  *****
>> 
>> Dear Chai Choon-Lee
>> 
>> I would recommend that, rather than pursue an SNA solution (if there is
>> one), you look at System Dynamics.  This explores the dynamics of flows
>> and the accumulation and dissipation of resources (or stocks as they are
>> called) over time. You indicate this is what you are wanting to do.
>> 
>> There are a number of sftware packages: Stella or IThink, Vensim, and
>> Powersim are the most popular: the first two are basically the same
>> product, but are aimed at the schools/education market and the commercial
>> market respectively.  There are student and run-time only versions from
>> publisher's web sites.
>> 
>> THE text at present is Sterman. J, 2000,"Business Dynamics: Systems
>> Thinking and Modelling for a Complex World", McGraw-Hill.  A more
>> approachable text is  Maani, K. E. and Cavana, R. Y., 2003, "System
>> Thinking and Modelling", Pearson Education.  Both books come with CDs
>> holding models in the various s/w packages as well as run-time versions
>> of the software.
>> 
>> And I would recommend, even though it is designed for K12 schools in the
>> US, the  site www.clexchange.org.  This has some superb introductory
>> papers, and models showing "simulation" possibly to undergrad level.
>> 
>> Then you can make an informed decision!
>> 
>> Best wishes ..
>> 
>> 
>> Roy Greenhalgh
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Quoting Chai Choon-Lee <[log in to unmask]>:
>> 
>>> *****  To join INSNA, visit http://www.insna.org  *****
>>> 
>>> Hello,
>>> 
>>> I am new to SNA. I am working on an engineering project that studies the
>>> interdependency among critical infrastructures, such as electricity,
>>> water, hospital, telecommunication, power plants, etc. I am exploring
>>> the  possibility
>>> of using SNA software to simulate infrastructure interdependency.
>>> 
>>> Infrastructure interdependency gives rise to an infrastructure
>>> network. In this
>>> project, apart from studying the structural characteristics of
>>> infrastructure network, such as centrality etc., I am wondering if there
>>> is any SNA software that can be used to simulate, for instance, the
>>> material/info/energy flows between infrastructures during an
>>> emergency/disaster situation?
>>> 
>>> From my shallow reading of SNA, I get a sense that SNA deals less
>>> with dynamic
>>> situations where different variables change as time goes by. For
>>> instance, in a
>>> disaster situation, medical supplies/hospital beds/food, etc. run down
>>> as the clock ticks, can we use SNA software to simulate this?
>>> 
>>> Sorry if my questions sound silly. Thank you for your time.
>>> 
>>> Sincerely,
>>> 
>>> Choon-Lee Chai
>>> Dept of Sociology
>>> University of Saskatchewan
>>> 
>>> _____________________________________________________________________
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>> 
>> _____________________________________________________________________
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>
>
>
> --------------
> David Krackhardt, Professor of Organizations, editor of JoSS
> Heinz School of Public Policy and Management, and
>   The Tepper School of Business
> Carnegie Mellon University
> Pittsburgh, PA 15213
> 412-268-4758
> website: www.andrew.cmu.edu/~krack
>   (Erdos#=2)
>
> _____________________________________________________________________
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