This part of OPC Unified Architecture (OPC UA) defines the PubSub communication model. It defines an OPC UA publish subscribe pattern which complements the client server pattern defined by the Services in IEC 62541-4. See IEC 62541-1 for an overview of the two models and their distinct uses. PubSub allows the distribution of data and events from an OPC UA information source to interested observers inside a device network as well as in IT and analytics cloud systems. This document consists of " a general introduction of the PubSub concepts, " a definition of the PubSub configuration parameters, " mapping of PubSub concepts and configuration parameters to messages and transport protocols, " and a PubSub configuration model. Not all OPC UA Applications will need to implement all defined message and transport protocol mappings. IEC 62541-7 defines the Profile that dictate which mappings need to be implemented in order to be compliant with a particular Profile.