-**Definition type**: they define when to read from and write to mqtt, when to update tokens, and when to call or invalidate attributes. there will be a small DSL to define those
-**Connection**: on instance/AST-level, an mqtt-topic can be associated to a source or target of a definition
-**Transformation**: a method or attribute modeling a math. function y = f(x)
-**Operator**: the atomar building blocks of a transformation, e.g., projection of an object, or a boolean operator
