allow user to enter equation used to evaluate telemetry data

Question

I currently have sensor data being dumped into a database. This is raw data, and needs an equation applied to it in order for it to make any sense to the end users. The problem I have, is that I do not know most of the formulas yet, and would also like the program to be flexible enough that when a new sensor is added to the system, the user would be able to enter in the calibration equation that would be able to convert the raw data into something useful.

I have never worked with letting a user enter in an equation to manipulate data. I would appreciate any input that might help. What direction should I be looking, should I be trying out lambda expression trees, evaluating the equation and compiling it using CodeDom, or looking in another direction? I have never done much with either lambda expression trees or CodeDom, and like always and on a fairly tight schedule, so the learning curve does count. I will have the opportunity to go back and make it better at a later date, they just need it up and running for now.

Thanks for any input.

Answer 1

I think you need to see what works for you. I also thought of the two only to find out you have mentioned them. I think the other alternative is to allow for parameters of a few major formulae to be stored (i.e. cubic, quadratic, exponential, log, ...) and one selected as the one to be used.

I would personally use the expression trees because it is the cleanest. One problem with CodeDom is the memory leak caused by compiling code especially if the user changes the code and builds the formula multiple times. One solution would be to load the compiled code in a separate AppDomain and then unload the whole appdomain.

Answer 2

I highly recommend FLEE for expression parsing/evaluation. It has a custom IL compiler that emits fast IL that doesn't have the memory problems that CodeDOM has.

It also has the desirable attribute of being easy to code with and extend.