LonMark® International and Interoperability
The LonWorks® protocol’s data-driven model is the foundation for interoperability, and LonMark® International is instrumental in facilitating interoperability.
The LonMark International industry association organizes task groups that combine groups of network variables into functional profiles. When functional profiles are voted in by association membership, they become part of the standard that can then be used by multiple device manufacturers to ensure their devices will interoperate on a network. 
For example, one manufacturer makes a temperature sensor, another makes a boiler controller, and a third makes a user interface for controlling a setpoint. In the LonWorks model, each of these devices is separate and can be used for multiple purposes. The networked application is created by binding the network variables that one device publishes to the input network variables that another device can subscribe to. In this way, a control application is created and new applications can be created from it. For example, a light sensor that provides information to the lighting system in an office can also be used to inform the automatic window blinds.
LonMark International has also standardized on conventions for large file transfers such as data logs, large provisioning data blocks, and others.
To see the list of over 500 LonMark certified products go to the LonMark Certified Products Database.