IEC 61158-3-4:2019 defines the services provided to the Type 4 fieldbus application layer at the boundary between the application and data-link layers of the fieldbus reference model and systems management at the boundary between the data-link layer and systems management of the fieldbus reference model. This third edition cancels and replaces the second edition published in 2014. It constitutes a technical revision. The main changes are: -Additional user parameters to services; -Additional services to support distributed objects; -Additional secure services