UC13: Representing WDCGG Data Flags

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Context:
GAW data centers, e.g., WDCGG, commonly report flag variables i.e., ORG_QCflag and QCflag. The latter contains information on both airmass origin and measurement quality.

short_name = ORG_QCflag
long_name = original_quality_control_flag
standard_name = quality_control_flag
comment = Details of original data quality control flags should be specified by contributors in metadata.

short_name = QCflag
long_name = quality_control_flag
standard_name = quality_flag
comment = 1 Valid (background) data considered 'background'
2 Valid data considered valid other than 'background,' or all valid data without categorization
3 Invalid data considered unfit for use (questionable/erroneous/absent data)
Details of correspondence between original data quality control flags and WDCGG data flags should be specified by contributors in metadata.

Challenges:
Properly capturing data flags in WIGOS metadata—especially the dual-purpose flag, i.e., QCflag, since airmass classification is derived from atmospheric filtering, not the instrument itself.

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Gemini assessment:

Both schemas can be adjusted to properly accommodate dual-purpose and harmonized flags like WDCGG's QCflag:

For wmdr2-bundled.json: Add a derivedFrom attribute to map QCflag back to ORG_QCflag, and use a structured flagDefinitions block capable of unpacking multi-dimensional flags (assigning both a quality status and an airmass classification to a single flag integer).

For WMDR2.pdf: Leverage ReportingProcedure to formally define both the correspondence mapping (ORG_QCflag -> QCflag) and the post-processing filtering algorithms used to classify baseline airmasses, keeping analytical data filters cleanly separated from physical instrument hardware.

Flag Requirement	Bundled GeoJSON (wmdr2-bundled.json)	Proposed WMDR 2 Domain Model (WMDR2.pdf)
Flag Translation Mapping (ORG_QCflag $\rightarrow$ QCflag)	Add derivedFrom or flagMapping property to link flag streams.	Formally document translation and harmonisation rules in ReportingProcedure.
Dual-Purpose Flag Semantics (Quality + Background State)	Add a multi-attribute flagDefinitions block to define compound meanings.	Map composite flag definitions to controlled vocabularies within ReportingProcedure.
Post-Processing Origin vs. Instrument State	Disconnects flags from processing methods in a flat property list.	Isolates data filtering workflows in ReportingProcedure apart from Equipment metadata.