IWXXM-US schemas cannot use IWXXM types

[mgoberfield]

Currently IWXXM-US 3.0 metarSpeci schema uses the following XML types in the IWXXM namespace (defined as "http://icao.int/iwxxm/3.0" with prefix 'iwxxm'):

• MeasureWithNilReason
• LengthWithNilReason
• RelationalOperatorType
• CloudAmountReportedAtAerodromeType
• AerodromePresentWeatherType

An XML document cannot refer to two different URIs having the same namespace prefix, in particular 'iwxxm'. The duplicate namespace prefix error will occur when IWXXM 2012-2 (defined as "http://icao.int/iwxxm/2021-2") is released and attempts to use it (or any other future release) to construct US IWXXM METAR and SPECI reports which have extension content in them. This will make the XML document invalid.

Therefore, the IWXXM-US schemas will have to duplicate the IWXXM XML types listed above but under the IWXXM-US namespace. This necessitates an IWXXM-US 3.1 release.

[mgoberfield]

E-mail communication from Mark Zettlemoyer, NOAA/NWS Liaison to FAA NextGen (AFS24) dated 27 April 2021, Subject: "IWXXM 2021-RC1 testing":

[Y]ou can still unilaterally act. That IWXXM document I drafted is now part 3 of FMH-13, but the update has only just made its way from the Obs Data (OD) WG to their parent Committee for Operational Processing Centers (COPC). Still a ways to go before it’s in effect.

Based on this permission to proceed from AFS (and if there is no objection from WG/OD after MZ briefing on this), I will make the required changes to common and metarSpeci schemas as version 3.0.1 and push them to the website before the NGITWS's IWXXM APIs are online. The changes are transparent to data producers and consumers. No change to NGITWS software.

[mdzettlemoyer]

I briefed the ICAMS Working Group for Observational Data (WG/OD) today (10 June 2021) on this issue. We can proceed with the namespace prefix update.

[mgoberfield]

Required changes merged.