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.