transforming from TN to ITN or vice versa

[daniel8an]

Dear Team,

Thank you very much for this amazing tool! we very much enjoy utilize it. I have a question regarding the transition from TN to ITN, or vice versa, once one of them has been implemented.

In the WFST tutorial, it was mentioned that, for constructing a TN system, you can generally achieve this by inverting your existing graphs (consider using pynini.invert) and making output changes to resolve indeterminacy (choosing a canonical output for each class).

While I can see the 'ru' language ITN implementation achieved broadly using the invert() function on the TN WFST, it appears that 'fr' language has distinct implementations for both TN and ITN.

I'm a bit puzzled about why some languages still support only one of the pair (TN/ITN) if the transition is relatively straightforward using the "invert" function. I tried to find answers online but was unsuccessful. Any guidance you could provide on this matter would be greatly appreciated.

Thank you sincerely.