Re: a union is always a join!

Vladimir Odrljin writes:

>I would like to make the following note.
>In my model (see www.dbdesign11.com) I didn't use terms as "possible
>worlds", "state of affairs" or "temporal". Especially I didn't use the
>mentioned terms as basic. They are undefined terms. For example,
>nobody knows what "world" is. However I precisely defined the state of
>entity and state of relationship which are some of my basic terms.
>Reinier for example doesn't distinguish "state of affairs" from the
>state of entity. He wrote about my model the following: "The database
>records not only present state of affairs, but also all past state" -
>meaning that db records something like "possible worlds" + all past
>states.

No, just the present state and all past states. I don't understand why you split a state of affairs out into states of individual entities and relationships. Those states must at all times form a consistent whole, and that whole is what I called the state of affairs. For databases that only hold information about the present, a state of affairs simply corresponds to the database contents. But this is really just a manner of speaking, the relationship between your model and relational databases can be described in terms of transformations that don't depend in any way on how the data in databases are interpreted.

[...]

>You seem to spending a lot of energy using basic terms and ideas from
>my db model.
>But you proclaim superiority of the relational model and it is unclear
>to me why you don't use basic terms from relational model or maybe
>from a combination of "temporal" data and relational model?

I can't answer this, but the converse is unclear to me, namely, why you don't just formulate your ideas in terms of working with ordinary relational databases.

>Vladimir Odrljin

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