IEC PAS 63166:2018(E) This book 7 defines several LED modules. Each LED module has a rectangular shape and the only restriction to the light emitting surface is that no light is emitted in the direction of the reference plane of the LED module.
This Book 1 defines the common concepts that underlie the Zhaga interface specifications.  In addition, this Book 1 specifies general requirements for Zhaga compliant LED Light Engines, associated components and Luminaires.