Table.write does not know how to deal with foreign keys about clldutils HOT 4 CLOSED

Yes, the w3c spec support composite foreign keys. Generally, I think, it is best to not regard "foreign key" as some sort of column type, but follow the "constraint" paradigm: i.e. "foreign keys" is a list of constraints on the values of a row, rather than a core property of the individual columns. Thus it shouldn't interfere with writing at all, but will come into play only when calling a dataset's validate method.

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So if we want to add more support for handling of foreign keys, we may want to introduce Constraint objects, pretty much like SQLAlchemy does it.

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How are you currently handling foreign keys to languages.csv etc.? I could not find an example and have therefore no idea what they should look like

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Ah, now I see. I shall adapt the script I sent you. I had – once again – misunderstood what needs to go there, but after adding an explicit LanguageTable I see how that is implemented and now I understand how Foreign Keys should be specified in the metadata json, and that they are actually separate from the columns.

Their semantics (constraints, 1:n, uniqueness, …) is an entirely different issue, and I'm fine with it not being specified at the moment.

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