I was already with you on the other points. And, technically, you can look at a relation as a dynamic homogenous map, and that's not wrong per se. But there se

I was already with you on the other points. And, technically, you can look at a relation as a dynamic homogenous map, and that's not wrong per se. But there seem to be some relevant points left out. First of all, a relation is a set of tuples. You can say that a set is just the degenerate case of a dynamic homogenous map in which the values are empty and you use only the keys. That seems like a useless generalization though, and more likely to cause confusion than clarity. Let's say you have a simple relation of person to product: this person has bought this product. It would be awkward to try to group them like: "this person has bought these products" because you could just as well invert it to "this product has been purchased by these people" and there's not a good reason to choose one over the other. Making it arbitrarily asymmetrical just makes it harder to reason about, so that's not a good choice. And neither attribute is unique. So, you are left saying that the key is {person, product} and the value is empty (or "unit", if you prefer). And yes, that is the key of the relation, so that's not wrong. But what have we gained through this exercise? We are calling a binary relation a "map", but confusingly it's not a map of the first attribute to the second -- it's a map of both attributes to nothing! You could say that relations representing something more map-like are common enough. But even in that case, it's common to have multiple candidate keys (which can be true even for normalized relations), and it's hard to say what's mapping to what. Again, more confusion than clarity. I think it's best to just call a relation the set of all tuples which satisfy the relation predicate. That's the model.