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New proposal on IWXXM versioning
--- (First created on 15 Feb 2021. Revised on 10 Mar 2021). Discussion has closed. See the minutes for details of the discussion and outcome ---
The previous Package Compatibility Table shows the IWXXM versions of a report that can be used to demonstrate compliance to a specific amendment of ICAO Annex 3. While the versioning of IWXXM follows Version Policy, the fact that in each update not all packages will be changed is creating confusions to both information producers, consumers and software developers. This page describes a slight change to the versioning of IWXXM and its packages with a view to reduce such confusion for all stakeholders.
Currently the version number of individual package is inherited from IWXXM. So even though some packages have not been changed in an update they will receive a new version number. This is also the reason why we need a Package Compatibility Table. There are a few identified issues with this approach:
- Strictly speaking the adopted Version Policy does not apply at package level.
- More mature packages rarely need changes, but as it is anticipated there will be a lot of new developments in IWXXM to support operation in future SWIM environment, their version numbers will advance frequently, so do the list of compatible versions of these packages in the Package Compatibility Table.
- While the information model remains the same across compatible packages of a report with different version numbers, the encoding and decoding software will inevitably take into account the handling of presence of multiple schemas during processing.
A slight modification to the existing approach is proposed as follow:
- Individual IWXXM package will have its own version number independent from other packages and IWXXM as a whole.
- Individual IWXXM package will be changed, and hence has its version number advanced in accordance to the Version Policy, as necessary.
- IWXXM now regarded as a collection of packages will have it own versioning methodology: In order to discriminate from the version numbers of its packages, and to tie in more closely with the ICAO Annex 3 amendment and WMO approval cycles, it is proposed to name an IWXXM version with the WMO Fast Track approval occasion (e.g. 2021-2 for the second Fast Track approval occasion in 2021).
The following is a fictitious example on the relationship of ICAO Annex 3 amendments, WMO approval occasion, IWXXM version and individual packages' version:
"IWXXM 2032-2 (containing packages METAR/SPECI v3.1, TAF v3.1, SIGMET v4.0, AIRMET v4.0, TC Advisory v4.1, VA Advisory v4.1, SW Advisory v3.1, WAFS SIGWX Forecast v1.0) has been approved by the second WMO Fast Track procedures in 2032 to meet the requirements of Amendment 83 to ICAO Annex 3 applicable in Nov 2031."
Note that we still need the compatibility table, but in this case each package will only have a single version for each ICAO Annex 3 amendment:
| ICAO Annex 3 | METAR/SPECI | TAF | SIGMET | AIRMET | Tropical Cyclone Advisory | Volcanic Ash Advisory | Space Weather Advisory | WAFS SIGWX Forecast |
|---|---|---|---|---|---|---|---|---|
| Amendment 76 (IWXXM 1.1) | 1.1 | 1.1 | 1.1 | N/A | N/A | N/A | N/A | N/A |
| Amendment 77 (IWXXM 2.1) | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | N/A | N/A |
| Amendment 78 (IWXXM 3.0) | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | N/A |
| Amendment 79/80 (IWXXM 3.1) | 3.1 | 3.1 | 3.1 | 3.1 | 3.1 | 3.1 | 3.0/3.1 | 3.1 |
| Amendment 81 (IWXXM 3.2) | 3.1/3.2 | 3.1/3.2 | 3.2 | 3.2 | 3.2 | 3.2 | 3.0/3.1/3.2 | 3.1/3.2 |
| Amendment 82 (IWXXM 3.3) | 3.1/3.2/3.3 | 3.1/3.2/3.3 | 3.3 | 3.2/3.3 | 3.2/3.3 | 3.2/3.3 | 3.0/3.1/3.2/3.3 | 3.1/3.2/3.3 |
| Amendment 83 (IWXXM 4.0) | 3.1/3.2/3.3/4.0 | 3.1/3.2/3.3/4.0 | 4.0 | 4.0 | 4.0 | 4.0 | 3.0/3.1/3.2/3.3/4.0 | 3.1/3.2/3.3/4.0 |
| Amendment 84 (IWXXM 4.1) | 3.1/3.2/3.3/4.0/4.1 | 3.1/3.2/3.3/4.0/4.1 | 4.1 | 4.1 | 4.0/4.1 | 4.0/4.1 | 3.0/3.1/3.2/3.3/4.0/4.1 | 3.1/3.2/3.3/4.0/4.1 |
| ICAO Annex 3 | METAR/SPECI | TAF | SIGMET | AIRMET | Tropical Cyclone Advisory | Volcanic Ash Advisory | Space Weather Advisory | WAFS SIGWX Forecast |
|---|---|---|---|---|---|---|---|---|
| Amendment 76 (IWXXM 1.1) | 1.1 | 1.1 | 1.1 | N/A | N/A | N/A | N/A | N/A |
| Amendment 77 (IWXXM 2.1) | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | N/A | N/A |
| Amendment 78 (IWXXM 3.0) | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | N/A |
| Amendment 79/80 (IWXXM 2021-2) | 3.1 | 3.1 | 3.1 | 3.1 | 3.1 | 3.1 | 3.0 | 1.0 |
| Amendment 81 (IWXXM 2023-1) | 3.1 | 3.1 | 3.2 | 3.2 | 3.2 | 3.2 | 3.0 | 1.0 |
| Amendment 82 (IWXXM 2026-1) | 3.1 | 3.1 | 3.3 | 3.2 | 3.2 | 3.2 | 3.0 | 1.0 |
| Amendment 83 (IWXXM 2029-2) | 3.1 | 3.1 | 4.0 | 4.0 | 4.0 | 4.0 | 3.0 | 1.0 |
| Amendment 84 (IWXXM 2032-2) | 3.1 | 3.1 | 4.1 | 4.1 | 4.0 | 4.0 | 3.0 | 1.0 |
We may need to take care of the following:
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Currently, users are discouraged to use the packages in a standalone way; one should first import iwxxm.xsd which will then import the rest of the packages. If we allow users to use selected packages only, then we will have to make sure that during each import of a package's XSD it will subsequently import all necessary packages. There will inevitably be multiple loading of the same schemas when more than one package is being used, but because packages are identified by their namespaces that should not be a significant issues for well implemented XML engines.
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At the WG-MIE/7 meeting, a question was raised asking whether there could be cases that a new IWXXM version will be published without new (regulatory) requirements. The answer is yes; even though we will try to introduce planned model changes together with a change in requirements which happened to occur in every Annex 3 amendments, we cannot rule out the occurrence of external changes (e.g. on the packages IWXXM is dependent on like GML, AIXM, etc.) or urgent bug fixes that has to be done prior to the implementation of next group of requirements. A slightly revised table in the new versioning approach to better describe these cases (see the last line) may look like the following:
| IWXXM Version | Compliance | Reason for Release | METAR/SPECI | TAF | SIGMET | AIRMET | Tropical Cyclone Advisory | Volcanic Ash Advisory | Space Weather Advisory | WAFS SIGWX Forecast |
|---|---|---|---|---|---|---|---|---|---|---|
| 1.1 | Amendment 76 | New Requirement | 1.1 | 1.1 | 1.1 | N/A | N/A | N/A | N/A | N/A |
| 2.1 | Amendment 77 | New Requirement | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | N/A | N/A |
| 3.0 | Amendment 78 | New Requirement | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | N/A |
| 2021-2 | Amendment 79/80 | New Requirement | 3.1 | 3.1 | 3.1 | 3.1 | 3.1 | 3.1 | 3.0 | 1.0 |
| 2023-1 | Amendment 81 | New Requirement | 3.1 | 3.1 | 3.2 | 3.2 | 3.2 | 3.2 | 3.0 | 1.0 |
| 2026-1 | Amendment 82 | New Requirement | 3.1 | 3.1 | 3.3 | 3.2 | 3.2 | 3.2 | 3.0 | 1.0 |
| 2029-1 | Amendment 83 | New Requirement | 3.1 | 3.1 | 4.0 | 4.0 | 4.0 | 4.0 | 3.0 | 1.0 |
| 2032-2 | Amendment 84 | New Requirement | 3.1 | 3.1 | 4.1 | 4.1 | 4.0 | 4.0 | 3.0 | 1.0 |
| 2033-1 | Amendment 84 | Urgent bug fix | 3.1 | 3.1 | 4.2 | 4.2 | 4.0 | 4.0 | 3.0 | 1.0 |
The benefit of using the proposed versioning is obvious: When you are operating a system with IWXXM WAFS SIGWX Forecast v1.0 implemented you are good from Amendment 79/80 up to Amendment 84. Of course when your system implements all IWXXM packages you will only need to mention IWXXM 2032-2 to demonstrate compliance to Amendment 84.