ITU-T Z.302 PDF

Introduction Syntax diagrams are a method of defining language syntax¹⁾. A syntax diagram consists of terminal and nonterminal symbol boxes connected by flowlines. An annotation symbol is used to insert comments. The syntax of a language can be defined by a series of syntax diagrams, each diagram defining a particular non-terminal symbol. In the MML Recommendations, syntax diagrams are used to assist in specifying the syntax of the MML input, MML output and the user-system dialogue procedures. A path through a syntax diagram defines an MML input, an MML output or a man-machine dialogue structure.

The sequence of symbols in a path through syntax diagrams does not always imply a corresponding order in time or in place. The order in time is only significant in dialogue procedures for changes in the direction of the information flow, i.e. from input to output or from output to input. For output on printers it represents an order in place (from left to right and from top to bottom). However, for output on VDTs, the order in place only applies to positions within a screen window (see Recommendation Z.322).

The following describes the use of syntax diagrams and states a set of rules for their use.

¹⁾ The syntax diagrams used in MML are based on those used to describe the programming language PASCAL [1].