Re: The Foundation of OO (XDb)

FYI Here is one possible way to represent your scenario in existing RDBMS

Table: MediaItem

Now, some DB's could allow the content to be in the table itself. However, if we don't want to assume that we have such support, then referencing a file (and path) is a practical way to do it. (This is not the ideal, but it works with most existing systems.)

I am not showing the Representation table here, but it would store information about the various formats, including version numbers, etc. It could also store player or driver info/locations.

A media player could use all this info to fetch and play the needed movie (production).

Multimorphism!

>
> Logically, a Video has a sequence of frames (pictures) and a stream of sound
> waves and everything necessary to synchronize them. Physically, though, we
> have many ways to represent Video. QuickTime, AVI and MPEG jump to mind.
>
> QuickTime, AVI and MPEG are not subtypes of Video; they are different
> representations or encodings of the same type. Logically, they perform the
> same function perhaps with different performance and size characteristics.
>
> Date's and Darwen's model of type allows the dbms to deliver all possible
> representations of Video at the logical level regardless of the actual
> representation stored on the physical medium.
>
> Someone in the creative department querying the dbms might watch a Video in
> its QuickTime representation on their Mac. Someone it the engineering
> department querying the same dbms might watch the same Video in its MPEG
> representation on their unix workstation. Someone else might watch it as an
> AVI in Excel.
>

-T- Received on Mon Jun 17 2002 - 06:57:14 CEST