This Recommendation defines the object-oriented data features of the Specification and Description Language. The features defined in this document include: polymorphic object-oriented data including virtual methods@ multiple inheritance of abstract types@ run-time type identification and type coercion@ as well as accessing data values by references. Without these features the language would afford limited scalability and be unsuitable for the definition of real-time embedded software applications. For this reason@ specifications in the Specification and Description Language use ITU-T Z.107 features. Together with [ITU-T Z.100]@ [ITU-T Z.101]@ [ITU-T Z.102]@ [ITU-T Z.103]@ [ITU-T Z.104]@ [ITU-T Z.105] and [ITU-T Z.106]@ this Recommendation forms a reference manual for the language.