[wenc]

Yes, you're correct -- an omission on my part. You need "valid time" (otherwise it's just "uni"-temporal modeling).

Thank you for the link to Snodgrass' book. I've not seen a formal book on temporal modeling in SQL before, so this is fascinating.

[jacques_chester]

Glad I could help! The research seems to have puttered on for a while after this book was written, but appears to fizzle out by around the turn of the millennium.

Some notion of bitemporalism showed up in SQL 2011, but somewhat constrained compared to what Snodgrass describes.