Use of deprecation in IWXXM

[blchoy]

We promised (https://github.com/wmo-im/iwxxm/wiki/Common-approaches-accross-exchange-models) but we did not put deprecation information in IWXXM 3.0RC1. We shall do this in subsequent releases.

Thanks Eddy (@porosnie) for pointing out.

[blchoy]

As I take a deeper look, I am not too sure the methodology can be easily applied in the case of IWXXM. As one may aware, IWXXM is governed by ICAO and WMO and it has to align with the amendment cycle of the regulatory documents which is ICAO Annex 3 and WMO No.306. Take Amendment 78 to ICAO Annex 3 as an example. It was approved by ANC at around May 2018 and will become applicable by Nov 2018. Once a feature was removed in Amendment 78 it should not be used from Nov 2018, and it should not even exist in the latest version of document including the schemas. Don't forget approval to the schemas by WMO comes afterwards. To adopt the methodology of deprecation we may need to change either the approval or implementation processes or both, but any of them would be a huge change.

I think we need some time to discuss the way forward.

[blchoy]

A paper was presented on this topic at the joint ICAO WG-MIE and WG-MRI workshop and the participants agreed that the deprecation procedures would be considered only when necessary. This may occur when we have better procedures which both align with the existing ICAO Annex 3 amendment approval procedures and change management best practices.