Wirth-Syntax Notation:

In the second phase, an information structure is provided by which all application models can be described with the help of the language EXPRESS. This phase is called the logical layer, and its output includes the information, objects, entities, attributes, associations and conditions.

In the third phase, the physical layer, the data formats and data files are defined in the Bachus-Naur-Form of the Wirth-Syntax Notation (WSN). The latter is a common language known in computer science for describing compilers.