• name a property to store a value
• read and write the named property
• conditionally execute code based on the value of a property
• generate any number of “agent instances” from the template and run the simulation

This did not seem difficult at first, as we already had a simulation engine that was already built around these principles. I then ran right into the main problem: while we could easily write this kind of code ourselves in Javascript, the implicit requirement was that students could define the first three operations IN ANY ORDER within the context of our simulation engine. That meant I needed to write some kind of scripting language or sequencing method on top of it because the students don’t have access to Javascript, and we can’t generate compiled Javascript code from source in the browser due to hard security constraints.

There are a lot of things happening in this simulation engine already, and I was having trouble “reasoning” about the system. Not only did I have to think of sequencing the simulation engine, but I also had to sequence the student script engine on top of this sequence. I was getting lost in the wheels within wheels within wheels. So I made a bunch of maps to get the systems out of my head and onto paper so I could reason by mentally visiting the system from different points of view. I used the web-based app Whimsical because it’s awesomely well-designed and lets me get really fussy about lining things up. (more…)