in reply to comparing sentences

With your description as given, I'd be hard pushed to come up with any approach; or even rule one out.

I think you would get far better responses if you supplied 3 further pieces of data:

  1. A sample template.

    If the real ones are proprietary, makes something up that is consistent with the real thing.

  2. A (complete) sample input where the user is "using the template".

    Along with an indication of how far through that sample you would visually determine that they were.

  3. A (complete) sample input where the user "is deviating from the template".

    Again, an indication of how much of that you would need to see before visually determining that they were not.

With that, you might get better, more targeted responses.

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