I recently had need to compare to OMT files to see what would be required for bridging them using VR-Exchange.  Rather than doing it by hand, which would have most likely been a large waste of time and risked missing something important, I spent a few hours writing a tool that would compare two OMT files for me.

One of the issues of comparing OMT files is that a simple text based diff won't give you the results you want because there is a lot of semantic information that needs to be compared.

The customer gave me two OMT files and said that they were both RPR FOM based with some extensions. That should simply work with VR-Exchange out of the box. However, using the OMTDiff tool we found that there were several enumerations with the same name, but with different values.  Using this information I was able to quickly create a modified HLA broker for VR-Exchange that intercepts these enumeration values and translates them properly.

This is one example of the realities that exist in the field that would have been excrutiatingly difficult to debug.  I have since saved myself (and hopefully you now) countless hours when dealing with the HLA FOMS and debugging translations between multiple FOMs.  I have placed the OMTDiff tool on the Bonus page for your diffing enjoyment.  The basic usage is (from the command prompt):

  • omtDiff.exe omt1 omt2
If you want to get really fancy you can capture all the output from the files by redirecting standard output to a file.  i.e.:
  • omtDiff.exe omt1 omt2 > output.txt
The output file is a list of the differences between each the two OMTs for each section.  It will compare enumerations, complex data types, classes, attributes, interactions, parameters, and notes showing any missing or different values or structures.