I suppose you inherit the sale object, do you know that you have 2 kinds of inheritance? With the first one the parent could access to the fields, methods... and with the second one, the parent couldn't.

1st kind of inheritance (From OpenERP Doc):

There are two possible ways to do this kind of inheritance. Both ways result in a new class of data, which holds parent fields and behaviour as well as additional fields and behaviour, but they differ in heavy programatical consequences.

While Example 1 creates a new subclass “custom_material” that may be “seen” or “used” by any view or tree which handles “network.material”, this will not be the case for Example 2.

This is due to the table (other.material) the new subclass is operating on, which will never be recognized by previous “network.material” views or trees.

Example 1:

class custom_material(osv.osv): _name = 'network.material' _inherit = 'network.material' _columns = { 'manuf_warranty': fields.boolean('Manufacturer warranty?'), } _defaults = { 'manuf_warranty': lambda *a: False, } custom_material()