IEC 62424:2016 specifies how process control engineering requests are represented in a P&ID for automatic transferring data between P&ID and PCE tool and to avoid misinterpretation of graphical P&ID symbols for PCE. It also defines the exchange of process control engineering request relevant data between a process control engineering tool and a P&ID tool by means of a data transfer language (called CAEX). These provisions apply to the export/import applications of such tools. This second edition cancels and replaces the first edition published in 2008. This edition constitutes a technical revision. It is a compatible extension of the first edition. The main changes and extensions are: - updated definitions and new definitions; - identification replaced with reference designation; - updated PCE categories and process functions; - CAEX version 3.0, introduction of: native multiple role support; - nested interfaces; - life cycle meta information; - a separate Attribute library; - updated examples; - updated electronic data model of the PCE request: new normative attribute library for basic PCE request attributes; - new informative extended attribute library for further PCE request attributes; - new informative electronic data model for the PCE request.