Recent rethinking of the Phonetics/Phonology-Interface has come to drop the old notion of a syntactic relationship between both research domains and replaced it by a semantic one. However, it remained relatively unclear how this relationship ought to look like. Progress in diagrammatic reasoning provides a fruitful approach towards a mutually constraining interface description. But to utilise this tool we first have to argue that it is reasonable to suppose a common ontology of a certain variant for both fiels of research. This is so, bacause the heterogenous logics-approach attempted here relies on the sharing of models.