This article is from the Object-Oriented Technology FAQ, by Bob Hathaway email@example.com with numerous contributions by others.
With Pick and its variants you only have problems if you want to
redefine an existing field. Because of the way the data are stored
and the separation of the data and the dictionary you can define
additional fields in the dictionary without having to do anything to
the data - a facility which we have found very useful in a number of
There is no general facility to redefine an existing field - you just
make whatever changes are required in the dictionary then write an
Info Basic program to change the data. We have seldom needed to do
this, but it has not been complicated to do.
If a field in the database is no longer used, it is often easiest
simply to delete the reference to that field in the dictionary, and
accept the storage overhead of the unused data. In such cases, while
the data cannot be accessed through the query language, (Pick)Basic
programs can still access them.
[Geoff Miller <firstname.lastname@example.org>]