 comment on column my_saved_specimens.modification_date_time is 'Last update date and time';
 create table template_classifications
        (
-        id serial not null,
         name varchar not null,
         name_indexed varchar not null,
         description_year smallint,
         description_year_compl char(2),
-        level_ref integer not null,
+        level_ref integer,
         status status default 'valid' not null,
         path varchar default '/' not null
        );
 comment on table template_classifications is 'Template table used to construct every common data in each classifications tables (taxonomy, chronostratigraphy, lithostratigraphy,...)';
-comment on column template_classifications.id is 'Unique identifier of a classification unit';
 comment on column template_classifications.name is 'Classification unit name';
 comment on column template_classifications.name_indexed is 'Indexed form of name field';
 comment on column template_classifications.description_year is 'Year of description';

comment on column people_taxonomic_names.person_name is 'Person name for the group concerned';
create table chronostratigraphy
       (
        eon_ref classifications_ids,
        eon_indexed classifications_names,
        era_ref classifications_ids,

comment on column chronostratigraphy.upper_bound is 'Upper age boundary in years';
create table lithostratigraphy
       (
        id serial not null,
        group_ref classifications_ids,
        group_indexed classifications_names,
        formation_ref classifications_ids,
