Recommendation ITUT Z.107 defines the object-oriented data features of the Specification and Description Language building on the foundation of the data definitions and expressions defined in Recommendation ITU‑T Z.104. Together with Recommendations 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 is part of a reference manual for the language. The language defined in this Recommendation partially overlaps features of the language included in Basic SDL‑2010 in Recommendation ITU‑T Z.101 and used in Comprehensive SDL‑2010 in Recommendation ITU‑T Z.102, and the features of Recommendations ITU‑T Z.103 and ITU-T Z.104.


The Specification and Description Language has concepts for behaviour, data description and (particularly for larger systems) structuring. The basis of behaviour description is extended finite state machines communicating by messages. Data description is based on data types for values. The basis for structuring is hierarchical decomposition and type hierarchies. Though a distinctive feature of the Specification and Description Language is the graphical representation, the data and expression language is textual. Features to encode and decode data communicated by channels, define data types with values and operations, variables (including parameters) based on data types and expression actions that use the data types have been defined in previous Recommendations. This Recommendation covers the features of the language used to provide object-oriented, hierarchical abstraction to allow the representation of larger and data-intensive systems. This Recommendation does not always provide a canonical syntax, but by applying the Model descriptions given, a specification can be transformed to Basic SDL‑2010 defined in Recommendation ITU‑T Z.101, except in those cases where additional abstract syntax is added in this Recommendation.


The Specification and Description Language is applicable within standards bodies and industry. The main application areas for which the Specification and Description Language has been designed are stated in Recommendation ITU‑T Z.100, but the language is generally suitable for describing reactive systems. The range of applications is from requirement description to implementation. The features of the language defined in Recommendation ITU‑T Z.107 are essential for scalable description of data-intensive systems using object-oriented abstractions.