If a <Property> tag has a type of ``supplierSpecific'' (or has no type defined) then it is viewed as being of an internal private type that is specific to IVES messages from the given Supplier. This enables Suppliers to link together elements within their own messages without having to conform to any 3rd party structure.
A value in a private property type can have a <SupplierSpecificProperty> element () associated with it. This gives the Supplier the opportunity to annotate the relationship between elements that share the same property value.