The term data model is describing the way how data is structured in an IED (Sever). This structure has several layers
Logical Device (LD)
Logical Node (LN)
Data Object(s) (DO)
Data Attribute(s) (DA)
Any interaction with an IED (Server) requires a reference to the data in the IED. Such a reference on the other hand is nothing else than the path through the different layers of a data model like so:
In essence nearly any service defined in the IEC 61850 either during configuration time or on runtime is utilizing such a reference. As such nearly every service does need to know the data model of the server it is communicating to. Or in other words services defined in IEC 61850 are depending on the data model definition. The data model therefore is an essential part!
The data model is the foundation for all services defined in the IEC 61850. It is therefore the basis for any IEC 61850 type comminication.