text: create sequence wrk_area.activity_s
  ;
  create table tgt_layer.activity
  (   activity_id integer   not null
  ,   start_ts    timestamp not null
  ,   end_ts      timestamp not null
  ,   source_id   text      not null
  ,   name        text      not null
  ,   description text      not null
  ,   primary key (activity_id, start_ts)
  )
  ;
  