The msgdiff tool does an HL7 syntax aware 'diff' between two sets of HL7 messages. The format of the input files is the same as for the HL7 Listener. Normally one just feeds in the two files of messages that you wish to compare.

Sometimes however you may be in a situation where you wish to compare two different mapping algorithms. Perhaps one might be done using Chameleon and another with another third party tool. In this case msgdiff supports the addition of a third message log file which is not diffed - but appears in the output feed. The "before" messages can be entered here and thus provide better context for how the other messages are generated.

This shows the syntax for invoking msgdiff:

msgdiff transformed.txt transformed2.txt before.txt

You should run the tool in a temp directory since it will output a bunch of HTML files. The main one is "index.html" which gives a list of all the messages, the number of differences found and a link to colorful report which shows the differences for each message.