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wmo-im / iwxxm

XML schema and Schematron for aviation weather data exchange
https://old.wmo.int/wiswiki/tiki-index.php%3Fpage=TT-AvXML
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Amendments (Annex 3, PANS-MET, etc.), IWXXM schema and WMO Codes Registry #148

Closed blchoy closed 3 years ago

blchoy commented 5 years ago

@marqh invited us to revisit this issue which seems to be pretty significant when we are moving away from legacy products.

Currently, changes in IWXXM schema and WMO Codes Registry are driven by Amendments to ICAO Annex 3. For legacy products linking up the Amendment number with IWXXM schema version number seems to be a natural choice (e.g. IWXXM 3.0.0 <-> Amendment 78). This is because further changes to the legacy Annex 3 products are promised to be rare and an increment in the IWXXM schema version number in association only with a change in the WMO Codes Registry but not the schemas may be a cost worthy way to do.

However, when we adopt an approach with generic schema as container of information and use more entries in the WMO Codes Registry to indicate what is in the container, there will be a need to label the versions of the schema and registry entries separately as they will evolve at different speeds. Furthermore, more documents are expected to trigger a change in IWXXM schemas and/or WMO Codes Registry including Annex 3, PANS-MET, etc., and we need to find a way to properly map these with the version numbers.

Inevitably, more metadata will have to be added to the registry to search entries valid for a particular version of the above documents (see #149 too). Views please?

blchoy commented 5 years ago

Looking at the content of a BUFR file (the one shown here is in BUFR Edition 3), Octet No.11 in Section 1 making reference to Common Code table C-0 for BUFR master table version number is probably something we may want to include in IWXXM instances to make sure that the right version of the table is being referenced, especially if references are being made to an older version of the table.

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Having said that, master table version number is not yet available on the WMO Codes Registry. Furthermore, the registry may also contain tables not being controlled under WMO No.306. Do we need a single mechanism to control all tables used by IWXXM? Or do we want to include metadata containing version number of all tables being referenced? May be @marqh can shed some light on this?

blchoy commented 3 years ago

This was superseded by the decision that TT-AvData will look after its own tables and https://github.com/wmo-im/iwxxm-codelists/issues/11 and is hereby closed.