Roman,

> Clear, I prefer the second solution, where
> "system-defined functions" cannot be overriden by the user.

I also agree. System functions are never to be overridden by user
functions.

If a user wants a different operation/algorithm, then they are free to
create a UDF which has a custom name.

At Broadview, all of our UDFs have a prefix 'f_' (as in 'f_StripDate()')
so that we clearly understand that the implementation is via UDF,
whereas 'StripDate()' would be a system defined function.

> P.S. Just came to my mind: can it be that you suggest to make the list
> of available system-defined functions (e.g. functions that are
> available without declaration) configurable on per-database level and
> provide a possibility to implement them in different languages?

I disagree with this notion.

An SDF is implemented within the engine, they are not external to the
engine. As such, they can be implemented in any language which the
engine build can support.

They are 'standard' as defined by the version of the Firebird engine,
they do not vary by database or by platform.


Sean