Good database design, variable number of attributes

Question

I\'m trying to create a database that contains a list of equipment. All of the equipment will have certain common attributes (such as manufacturer, model #, serial #, etc.), the

Answer 1

Options 1, 2, and 3 share one very serious flaw: you have to modify the underlying table schema when someone dreams up a new attribute. In the case of Option 1 the problem is compounded by the possibility that a new equipment type will be introduced. How sure are you that the set of attributes is fixed for all time? How happy will you be to take outages or tell the client that no, you can't have a new attribute?

If you are very likely to do queries off common attributes, you might try a hybrid of 3 and 4, with a dash of 2 thrown in splitting on attribute type rather than equipment type, which seems much more volatile. Option 4, if I understand correctly, is a normal form version of option 1 which solves all its inherent problems (sparseness and brittleness).

INVENTORY( id*, model, manufacturer, serial )
ATTRIBUTE( id*, name, type, description )
INVENTORY_FACT_STRING( inv_id*, attr_id*, value )
INVENTORY_FACT_NUMBER( inv_id*, attr_id*, value )
INVENTORY_FACT_LIST_STRING( inv_id*, attr_id*, ordinal*, value )

etc.