Dear Pat,
You said:
And I guess I have to defer to you when it comes to databases. But then I wonder why there has ever been a notion of, for example, a temporal database? After all, if database classes can change with time, why do we need to do anything special to make them 'temporal' ?
There are at least two things going on here. Firstly, the whole point of databases is that you can add records to them. Of course as soon as you do, in principle you have a different ontology (or whatever you want to call it). However, that is OK, because what you want is an ontology of how things are now.
[LEO:] Actually in the database world, one talks of the intensional database (the schema) and the extensional database (the rows/tuples). The closest equivalent to an ontology is the schema. With instances or facts being the rows. So the extension changes all the time, and one could even use the same schema for two different databases, which by definition have two different extensions. And though the schema does change over time, it doesn’t change often compared to the rows in tables.
MW: There is also in between stuff called master and reference data. This is data in tables that is at least slowly changing, much of it is classes, and many would consider this part of the ontology for the system, tailored to the particular implementation.
Regards
Matthew West
Information Junction
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