writing functions with return type record

Hi, i'am try to encapsulate some logic into funtions to clear design,

my question is:

CREATE OR REPLACE FUNCTION get_something(various param)
RETURNS SETOF mydummytable AS
$BODY$
DECLARE
v_rec mydummytable%rowtype;
BEGIN
FOR v_rec IN (select field1, field2 blabla)
LOOP
RETURN NEXT v_rec;
END LOOP;
RETURN;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;

with mydummytable a real empty table
i can use function in query like this

select field1 from get_something(...)

without creation of table mydummytable and use in function type RECORD

i can use
select field1 from get_something(...)a (field1 type, field2 type,...)

is possible and if yes how to write function return rowset or where
store mydummytable structure without create table mydummytable
and use function in query like this select field1 from
get_something(...) without a (field1 type, field2 type,...) definition

PS i read about resultset fully retrieve , my query in function at
maximum return one or two row