I need to develop a database to register clients. Each client can have
zero, one or more assigned "labels".
It is like the gmail label system or Thunderbird, where you define a
set of labels, and then you can assign one or more labels to a record.

Then, I want to filter the clients according the labels, just like
gmail or Thunderbird.

I am studying several options but I would like to know if somebody has
similar experience or simply an idea. I can use the latest version of
Firebird, maybe there are new functions that help me on this issue.

Thank you