select a.value as a,b.value as b1,c11.value as c11 from table_a as a 
      -- join b
      left outer join table_b as b on b.a_pk = a.pk 
            -- join c avec value = a_1
            inner join table_c as c11 on c11.b_pk = b.pk and c11.value = 'a_1'     
         
a	b1	c11
X	a	a_1


select a.value as a,b.value as b1,c11.value as c11 from table_a as a 
      -- join b
      left outer join table_b as b 
            -- join c avec value = a_1
            inner join table_c as c11 on c11.b_pk = b.pk and c11.value = 'a_1'     
      on b.a_pk = a.pk

a	b1	c11
X	a	a_1
Y	 	 


DROP TABLE table_b;
DROP TABLE table_a;

--Equivalent CompositeNetwork
CREATE TABLE table_a
(
  pk bigint NOT NULL,
  value character varying(1024),
  CONSTRAINT table_a_pkey PRIMARY KEY (pk)
);

--Equivalent TerminationPoint
CREATE TABLE table_b
(
  pk bigint NOT NULL,
  value character varying(1024),
  a_pk bigint,
  CONSTRAINT constraint_a_pk FOREIGN KEY (a_pk)     REFERENCES public.table_a (pk),
  CONSTRAINT table_b_pkey PRIMARY KEY (pk)
);

--Equivalent Characteristic
CREATE TABLE table_c
(
  pk bigint NOT NULL,
  value character varying(1024),
  b_pk bigint,
  CONSTRAINT constraint_b_pk FOREIGN KEY (b_pk)     REFERENCES public.table_b (pk),
  CONSTRAINT table_c_pkey PRIMARY KEY (pk)
);

insert into table_a values (1,'X');
insert into table_a values (2,'Y');

insert into table_b values (1,'a',1);
insert into table_b values (2,'b',1);
insert into table_b values (3,'c',1);

insert into table_c values (1,'a_1',1);
insert into table_c values (2,'a_2',1);

insert into table_c values (3,'b_1',2);