Home > STELLA & iThink > What is the difference between STELLA and iThink?

What is the difference between STELLA and iThink?

The question we get asked most frequently by just about anyone who wants to know more about our modeling software is “What is the difference between STELLA and iThink?”  From a functional perspective, there are no differences between the STELLA and iThink software — they are two different brands of the same product.

The STELLA brand is targeted toward individuals in educational and research settings.  Supporting materials such as An Introduction to Systems Thinking with STELLA and sample models cover the natural and social sciences.

iThink, on the other hand, is targeted toward an audience of users in business settings.  An Introduction to Systems Thinking with iThink is written with the business user in mind and model examples apply the software to areas such as operations research, resource planning, and financial analysis.

Aside from the different program icons and other graphic design elements that go along with branding, there are just a few minor differences in the default settings for STELLA and iThink.  These differences are intended to pre-configure the software for the model author.  They do not limit you in any way from configuring the default setup to match your own individual preferences.

Below is a list of all the differences between the default settings for STELLA and iThink.

Opening Models

When opening a model with STELLA on Windows, by default, the software looks for files with a .STM extension.  Similarly, iThink looks for files with an .ITM extension.  If you want to open an iThink model using STELLA or vice-versa, you need to change the file type in the Open File dialog as shown below.

STELLA file open dialog

On Macs, the open dialog will show both iThink and STELLA models as valid files to open.

If you open a model with a file type associated with the different product than the one you are using, you’ll get a message similar to the one below warning you that the model will be opened as “Untitled”.  Simply click OK to continue.

STELLA file conversion dialog

Saving Models

When saving a model in STELLA, by default, the software saves the model with a .STM file extension.  Similarly, iThink saves model s with an .ITM extension.  If you’re using STELLA and want to save your model as an iThink file or vice-versa, use the Save As… menu option and select the appropriate type as shown below.

STELLA save as dialog

STELLA on Windows save dialog


STELLA on Mac save dialog

STELLA on Mac save dialog

Run Specs

Since iThink is targeted toward business users who tend to measure performance monthly, the default Unit of time for iThink is set to Months.  It’s also easier to think about simulations starting in month 1 (rather than month zero) so we set the default simulation length in iThink to run from 1 to 13.  STELLA on the other hand, reports the Unit of time as “Time” and, by default, runs simulations from 0 to 12.

Run Spec comparison

Run Spec Default Settings Comparison

Table Reporting

In a business context, financial results are generally reported at the end of a time period and the values are summed over the report interval.  For example, in a report showing 2010 revenues we would assume the values reflect total revenues at the end of the year.  In line with this assumption, the default Table settings in iThink include reporting Ending balances, Summed flow values, and a report interval of one time step.

In a research setting, scientists tend to prefer reporting precise values at a particular time.   For this reason, the default Table settings in STELLA are configured to report Beginning balances, Instantaneous flow values, and a report interval of Every DT.

table default settings comparison

Table Default Settings Comparison

STELLA or iThink

When choosing between STELLA or iThink, try to think about the kinds of models you intend to build and the problems you are looking to solve.  If your objective is to drive business improvement, chances are iThink will be a better fit.  If your purpose is to understand the dynamics of a natural environment or social system, STELLA will likely be your brand of choice.  Whatever you decide, both products will provide you with the exact same functionality and can easily be configured to suit your own preferences.

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  • Bsginc

    Every time I read the discussion of the time function and DT, in iStella and iThink, I cringe. You talk of time frames that are appropriate to business and the social sciences as being 1 to 13 and 0 to 12, respectively.

    I cringe because those ranges appear to encompass 13 periods. At least when using language conventionally. That, of course, is really not the case as you are talking time periods that begin at a point and go TO a point, not THRU a point in time. Further, each point is exactly that, a point in time, not a period of time as is represented by the interval between two points.

    If you can’t wrap your head around this fundamental difference, understanding the description of time periods and the differences in how they are represented in iStella and iThink is a struggle.

    Because language is so imprecise, you might consider this point when attempting to explain both products to new users.

  • We have attempted to clarify this issue within a couple of other posts:

    – Why DT Matters: http://blog.iseesystems.com/modeling-tips/why-dt-matters/
    – Integration Methods and DT: http://blog.iseesystems.com/modeling-tips/integration-methods-and-dt/

    Hopefully, you and others reading these comments will find these articles useful.

  • Anonymous

    Difference at initial configurations could be handled as some default profiles beside user defined ones. It seems there should be other reasons for releasing and maintaining two different versions of the same product. Working on concepts and outsourcing software production will improve the product since at 2013 it seems like 1995 soft-wares…