Yeah, I've heard of Date and Codd. I've even read some of the former. I have felt moderately confident in my database knowledge. And then a recently published interview with Date has made it clear that I've committed the sin of listening to the majority rather than digging in for the facts. In particular, this passage simultaneously reveals my ignorance and makes me happy:
Object/relational DBMSs: To a first approximation, "object/relational" just means the domains over which relations are defined can be of arbitrary complexity. As a consequence, we can have attributes of relations--or columns of tables, if you prefer--that contain geometric points, or polygons, or X rays, or XML documents, or fingerprints, or arrays, or lists, or relations, or any other kinds of values you can think of. But this idea too was always part of the relational model! The idea that the relational model could handle only rather simple kinds of data (like numbers, and strings, and dates, and times) is a huge misconception, and always was. In fact, the term object/relational, as such, is just a piece of marketing hype
... As far as I'm concerned, an object/relational system done right would simply be a relational system done right, nothing more and nothing less.
There's quite a bit more where he tackles common misconceptions and how they contradict the relational theory. I believe I have another book to buy (though I'm still not certain how I feel about his objection to NULLs, but I'll read again what he has to say).
In other words, it turns out that much of what I've said about the relational databases was me being ignorant and being cocky about that ignorance. I'm more than a little embarrassed by this, but it's better that I just spit it out now.