Is there any example of how to define and use proprietary object properties?
Not that I'm aware of. Are you defined custom objects or just properties? I think (and I haven't tried it so I'm not sure) that adding your Objects into com.serotonin.bacnet4j.type.enumerated.ObjectType , your properties into com.serotonin.bacnet4j.type.enumerated.PropertyIdentifier , and their relationship with each other and transmittable data types into com.serotonin.bacnet4j.obj.ObjectProperties you will be well on the way. I didn't see any obvious ways for runtime modification of these mostly static classes and their relationships.