How to define missing values in a single field?

There are cases where a missing value in a column is a valid value in another column. For example, https://data.gov.au/dataset/colac-otway-shire-trees/resource/bcf1d62b-9e72-4eca-b183-418f83dedcea has a missing value for Year_Planted as 0, but that might be valid in another columns.

From https://frictionlessdata.io/specs/table-schema/, it appears missing values can only be defined on the table level, so this case can’t be defined in table schema.

[ashepherd]

Just wanted to add our use case for the missingValues property on a field. @BCODMO provides data management support for individual researchers on short-term funding (1-3 yrs) from NSF. Our researcher’s data can sometimes contain short-hand values that can be joined with lookup tables after they come back from sea. These fields are usually things like species names or quality flags that they abbreviate to save time during collection. There could be a scenario where a missing data value of ‘nd’ in one column might be a valid data value in another column. Having missingValues with a string of nd at the table-level can lead to NULL values in a column where nd might be a valid value for an abbreviated species name or quality flag.

[rufuspollock]

@vitorbaptista originally they were per field but we switched to per resource. I think it could make sense to support both and not complex to do so but i’d appreciate thoughts form @pwalsh