The IEC publishes a series of documents and rules governing the preparation of documents, drawings and the referencing of equipment.   Depending on country and industry, people are either familiar with the IEC system or not.  For those not familiar it can be a little confusing at first.

Often when IEC document production is compared to methods it is mistakenly assumed the difference is simply symbols.  This is not the case.  The IEC document and referencing system is a comprehensive approach covering symbols, drawing and layout techniques, equipment references, identification of terminals and signals, classification of documents and computer data organisation.   It also goes beyond just documentation and extends into physical devices and implementation.