Hi,
I have a database application running under sybase anywhere SQL server.
  I would like to develop modules in Ruby to access that database.

I started to look at ActiveRecord, but it seems that one requirement is
that all tables have an identity column with a specific name.    My
database was not designed that way :-(

Are there ActiveRecord alternatives that would allow me to use my
existing database design?  Or even better, are there reviews that
compare the different data layers available for Ruby?

Thanks,
Edgard