CCITT (now ITU-T) Specification and Description Language (SDL) and systems engineering (formal and informal) in SDL are considered in this publication. The latest version of the language, SDL-92 [ITU Z.100 SDL-92] is introduced.

Acknowledgements. Introduction. Intended usage. Overview of the book. Conventions of notation used in the book. 1. Specification of Telecommunications Systems. When to use SDL. What to describe in SDL. Limitations. Availability of SDL. 2. Overview of SDL. Introduction. Processes and process types. Specifying properties of variables. Specifying behaviour: states and transitions. Procedure attributes. Grouping objects: blocks of processes. Specifying systems: set of blocks connected by channels. Specialisation by adding attributes, states and transitions. Specialisation by redefining virtual transitions. Specialisation by redefining virtual procedures. Specialisation of signals. Classifying blocks: block types and specialisation of these. From partial to complete behaviour: composition of services. Diagrams and scope/visibility rules. Organising sets of related types: packages of type definitions. Summary. 3. Behaviour. Extended finite state machines. Processes. Communication. Contents of a process. Lifetime. The basics of a process. Other state triggers. Other actions. Procedure. Additional communication schemes. Modelling time. Examples. 4. Structure. Introduction. Structuring of systems. Parameterised types. Specialisation of types. Structuring of specifications. 5. Data. Introduction. General data concepts. The SDL data model. Structure of a data type definition. Use of literals and operators. Generators. Using built-in features. Use of data. Defining operators. Examples. 6. System Engineering. Engineering of systems. SDL use in methodologies. Creating SDL (using SPECS methodology). Integrating SDL into a complete methodology. Lexical rules: use of characters. Informal text. Errors and undesirable specifications. Support for SDL. Building on experience. A. Combining SDL and ASN.1 Principles for combining SDL and ASN.1. Summaries. B. Example: Using Processes as Pointer Types. Overview. The system. The list user block. The list handling block. The list element handling block. C. Differences between SDL-88 and SDL-92. Cases where SDL-92 is not compatible with SDL-88. Extensions compared to SDL-88. D. Syntax Summary. PR summary. GR summary. Symbol summary. Connectivity of SDL symbols. Index.