1. A method for performing a quantity takeoff computation, the method comprising: organizing a CAD drawing into a hierarchical representation that includes at least one object family associated with one or more object types, wherein at least one instance of at least one object type represents a drawing object present in the CAD drawing; receiving a selection of an object family; parsing the selected object family to determine the one or more object types associated with the selected object family; creating a takeoff object for each of the one or more object types associated with the selected object family; identifying instances of each of the one or more object types associated with the selected object family, wherein each instance is associated with one or more object properties; and quantifying the instances and the one or more object properties associated with each instance to produce a quantity takeoff value.