I implemented a [private] genealogical data entry system based on the GenTech data model, which has a "surety scheme" entity, designed to capture perceived unce

I implemented a [private] genealogical data entry system based on the GenTech data model, which has a "surety scheme" entity, designed to capture perceived uncertainty. I also added a "Fuzzy Date", where every date-like value was decomposed into all its constituent components (year, month, day, hour, ...), all optional. It could also capture a range of such fuzzy dates, so it was possible to enter a "date" such as "The first of a month no earlier than 1950 and before June 1990". There was a loooong list of validation constraints to attempt to prevent contradictions being entered, and I think I caught all the cases, but...