Abstract base table?

I am toying with the idea of deriving a couple of tables from a common table
(though I am aware that there are some oddities with the way postgresql does
inheritance). It should be possible to make entries into the derived tables,
but not into the base table (because it really just doesn't have enough
columns to be viable).

Ignoring questions as to the advisability of the design, is it possible to
check in a rule or a trigger function, which table it is exactly that is
being updated, the base or the derived?

Cheers,
Gerard.

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