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VORSIM software was developed and enhanced over many years as new models were developed with the system. From the author’s viewpoint, items were added to VORSIM to speed up and simplify tedious complex model building tasks. When a lot of work was done building a model; that led to the development of extensive backup and recovery features. This guaranteed that once information is entered in a model data or equation workbook, it can be restored easily. This means that if time-consuming work is done preparing a model; that work will not have to be repeated if you have been careful to back up data, equations, and workbooks as you go along. Other improvements came in response to diagnosing problems with invalid model equations or models that did not solve. Some developments involved improving existing control screen features such as ‘movelists’. Since VORSIM improvements were carried out over time, many of them are accessed by the VORSIM menu or forms rather than directly from the control screens. The general rule for development was “if a procedure saves time and/or improves accuracy, add it to VORSIM.

As you start using VORSIM, you will find a balanced pattern of operations (between VORSIM and Excel) that is comfortable for you. For example, the model manager has a routine to expand variables, etc. in a model. But experience plus knowledge of how range names operate led the author to instead expand models by manually changing things in the definition workbook and rebuilding the entire model over again. This is possible because if data and equations and associated workbooks are backed up, old data and equations can be automatically put back in the correct place in a revised model. The author’s experience is that a final model sometimes had to be totally rebuilt from the beginning several times before it is satisfactory. VORSIM makes this rebuilding process simple and fast. If equations have to be re-written with different parameters, VORSIM does it in a flash. If you have equations in spreadsheets with similar structures but differentiated only by different parameters, you can build a set of equations in one spreadsheet and literally copy it to other spreadsheets where parameters are changes – saving an enormous amount of time. Finally, it is crucial that a model-builder be able to quickly tell a convincing story about simulation results; here VORSIM tools are there to help instant post-solution analysis and the preparation of user designed reports. Since VORSIM runs in Excel, all the capabilities of the Excel spreadsheet are available at any time in any model workbook. In many cases, VORSIM is simply automating Excel features for the model builder.

Experiment with VORSIM and learn where the tools and features are and combine them with Excel features to get your models built. Using VORSIM well means knowing Excel, learning VORSIM features, and understanding model building. Hopefully VORSIM itself can help you learn more in all of these areas. As Excel changes with new versions, VORSIM must change also. The latest version 15 requires and takes advantage of Excel 2013. This requires a new file nomenclature but results in a faster and more powerful modeling system.

Vernon Oley Roningen – VORSIM Author