Glad to see all the ways people use them! Date and Darwen are clear-thinking and they write well. But you are right that they are quick to criticize and some o

Glad to see all the ways people use them! Date and Darwen are clear-thinking and they write well. But you are right that they are quick to criticize and some of the alternative solutions they offer are unconvincing. The most obvious example is their handling of NULL, which had a bunch of great criticisms followed by a totally impractical altenative ("special values"). If they had been a bit more humble, maybe they would have just borrowed Maybe/Option types from ML. On the other hand, they really helped me make the connection between logic and databases. And that helped me a lot in practical ways (e.g. exploring dirty data precisely). Regarding temporal data, they divorced from SQL and started from first priciples. That clarified a lot of things for me and then I adapted those ideas to SQL. So: their books are great, but I don't recommend joining their cult ;-) EDIT: I think a lot of SQL implementations are going about temporal the wrong way. They should focus on the fundamental building blocks first (like ranges of time) and build up from there.