A Day at "The Park" with ExtendSim

“Why are you collecting this data?”, I asked. It seemed a reasonable question given my current location. You see my friends and I were hiking to the top of Half Dome in Yosemite National Park, and we were currently about 7 miles from the trailhead. Imagine our surprise when a formally dressed college student (complete with official ID badge) asked us if we were willing to participate in a trail study. We were supposed to be in the middle of nowhere! But there she was sitting off to the side of the trail at a foldout card table that was holding a stack of time cards, a clipboard and some stickers.

“We’re trying to understand the traffic patterns along this route to Half Dome.”, she answered. "Participants show their time cards to officials stationed at various waypoints along the way. The officials will mark your time of arrival at each waypoint. Would you like to participate?”

“Perhaps.”, I said. “This sounds like you’re collecting data for a simulation study. Is that true?”

“Yes.”

“What simulation tool are you using?”, I asked.

“Umm….I think it’s called ExtendSim. Yeah. That’s it. It’s called ExtendSim.”

I smiled and said, “Well, in that case we’d be very happy to participate in your study.” ;-)

So the next time someone asks you, “Where is ExtendSim used?”, maybe the most appropriate response is, “Where is it not used?”

Simulation Master Class

Being a simulation modeler can often be a lonely proposition. Often alone, you are called on to build a model of a complex process, analyze that model, and present the results to management. As simulation modeling is as much an art as a science, we thought applying the musician/artist Master Class concept to simulation would be helpful to our customers. 

A team of simulation experts from a range of backgrounds have been invited to join the Imagine That Inc. technical staff to discuss their simulation techniques, general research, and specific ExtendSim features that they find intriguing. Some of the Master Classes will be specific to ExtendSim while others will be more general and useful to all simulation modelers.

We have a number of speakers lined up. However, if you are interested in presenting at one of our Master Class sessions or simply have some suggestions, let us know. We are looking for speakers who can address the issues of the simulation community as a whole as well as ExtendSim modelers.

Imagine That’s simulation Master Class sessions are open to everyone at no charge. Classes begin May 2011. Check our web site for more details.

Reviewing the Review

If you are evaluating simulation software, a third-party review or paper comparing the features of different simulation software programs can be very useful. However, not all software reviews are created equal. Some are truly excellent, well researched, informative, and accurate. Others contain factual errors, use outdated software, and are even sometimes biased by economic considerations of the author.

The gold standard for a comparison is Tom Schriber and Dan Brunner’s perennial “Inside Simulation Software: How it Works and Why it Matters”. This paper does not attempt to recommend one software product over another, but it does give insight into the inner workings of a variety of simulation packages. When Tom and Dan were including ExtendSim (Extend) into their paper, we exchanged nearly 100 emails detailing the precise behavior of our software. The authors have taken care to update the paper as new versions of ExtendSim have come out. There are other good reviews as well. I have not always agreed with their conclusions, but I do respect their methodology.

I won’t reference the paper on the other end of the spectrum. However, I did find 14 obvious technical errors in a little more than a page of text describing ExtendSim. These included the wrong web site, incorrectly stating that there were limitations on the number of levels of hierarchy, and even the product name was incorrect. The author never contacted us or asked us to comment on his review.

So, if you are looking at simulation software reviews, take the following steps to make sure that you are getting a thoughtful, accurate commentary:

• Contact the author and ask them if the paper was reviewed by the simulation software vendors before publication.
• Look for obvious technical errors. Generally, this is an indication that the author did not do their homework.
• Did they use the latest version of the software?
• Does the author have any connection with a simulation software vendor, currently or in the past?
• If you can, contact modelers who use the software in the paper. Ask if they agree with the conclusions.

As software developers, you can expect us to be biased towards our own creations. Unfortunately, you cannot always find that even in neutral third party evaluations. Caveat emptor.