Definition from IAI: The product type (IfcTypeProduct)
defines a list of property set definitions of a product and an optional set of
product representations. It is used to define a product specification (i.e. the
specific product information, that is common to all occurences of that product
type).
NOTE: The product representations are defined as
representation maps, which gets assigned by a product instance through the
representation item 'IfcMappedItem'.
A product type is used to define the common properties of a certain type
or style of an object that may be applied to instances of those products to
assign a specific style to them. Product types may be exchanges without being
already assigned to products.
HISTORY: New entity in IFC Release
2x.