If you’re looking for manipulate many2many and one2many fields in OpenERP (to link objects to each other or delete or modify this link), you must write one of these values to many2many or one2many field:

many2many:

(0, 0,  { values })    link to a new record that needs to be created with the given values dictionary
(1, ID, { values })    update the linked record with id = ID (write *values* on it)
(2, ID)                remove and delete the linked record with id = ID (calls unlink on ID, that will delete the object completely, and the link to it as well)
(3, ID)                cut the link to the linked record with id = ID (delete the relationship between the two objects but does not delete the target object itself)
(4, ID)                link to existing record with id = ID (adds a relationship)
(5)                    unlink all (like using (3,ID) for all linked records)
(6, 0, [IDs])          replace the list of linked IDs (like using (5) then (4,ID) for each ID in the list of IDs)

Example:
   [(6, 0, [8, 5, 6, 4])] sets the many2many to ids [8, 5, 6, 4]

one2many:

(0, 0,  { values })    link to a new record that needs to be created with the given values dictionary
(1, ID, { values })    update the linked record with id = ID (write *values* on it)
(2, ID)                remove and delete the linked record with id = ID (calls unlink on ID, that will delete the object completely, and the link to it as well)

Example:
   [(0, 0, {'field_name':field_value_record1, ...}), (0, 0, {'field_name':field_value_record2, ...})]