6.2.10 RTT Interoperability Note 0 about no requirement to document
In 6.2.10 about RTT Interoperability which was decided by STF614 and recorded in V2.1.8b_Integrated_Proposal_for_Key_RTT_provisions_and_tests.docx (and now integrated into the latest working draft) has a note 0 which looks very redundant and potentially contradicting regulation. I suggest to delete it. It cannot contribute to any clarity, just a little risk for contradictions in some cases.
This is the draft 6.2.10 with just Note 0
6.2.10 RTT interoperability
Where ICT provides functionality that allows continuous bidirectional voice communication and connects to another provider’s ICT that allows continuous bidirectional voice communication, the ICT’s documentation shall contain information on the main specifications by which RTT is implemented in a manner that allows the RTT on the ICT to interoperate with the other provider's ICT that it interoperates with for voice, using one of the following options:
a) Any set of specifications for RTT communication that would fulfil the RTT requirements in the present document that is mutually agreed upon between providers of the ICT and the providers of any other ICT with which it interoperates for continuous bidirectional voice communication.
b) ITU-T Recommendation T.140 [] for functions including coding and presentation and RFC 4103 [] updated by RFC 9071 [] for other aspects of RTT communication.
NOTE 0: There is no requirement above for documentation of connections between ICT or components from the same provider – only when ICT connects to ICT from another provider.
Reasoning: The precondition causes the requirement to be valid only for providers of ICT who have interoperability in voice with another provider.
The Note 0 explains this by repeating the same statement but with inverted logic, saying when documentation is not required. It looks very redundant and totally unnecessary. But it implies a slight risk for confusion. The precondition mentions one case when it is required to provide detailed documentation. There may be other reasons. The interoperability may have been ordered to be provided by regulation and the regulation requires documentation regardless of who are the providers having interop. It may be one provider who does initial implementation of both system and client, but future regulation may require the interface to be documented. Then the note seems to contradict that regulation. But the alert reader see that it does not. The note starts "there is no requirement above ..... . So it is true and it does not contradict any future regulation but it just makes reading and sorting out what is the real requirements harder.
Proposal: Delete Note 0
By the way, I do not think that who are first to implement solutions for an interface is a good qualification for requiring documentation or not. I think it is much more common that there are the intentions to have an open or closed interface that drives the decision to document the interface openly or not. But I dont want to argue for changes in the precondition and requirement now.