From Node Graphs to Knowledge-Graphs (and Ontologies) Using the class-based hierarchy and inheritance structure of the classes and methods underlying the nodes, their input and output field types, as well as their connections in the node graphs, an application-or domain-level ontology and knowledge graph can be automatically deduced from the node graphs as well, besides executable code. Again, the exact implementation will be very domain specific, but in our case, all connections between nodes represent a "is_used_by" respectively "uses_material_from" relationship. The only exception is the connection between 'Container' nodes and 'Chemical' nodes that represent a "contains_chemical" respectively "is_contained_in" relation. The node input parameters all represent a "has_property" relationship, while the type of the input variable associated with this field (e.g., a float, bool, container, chemical, volume, etc) represents a "is_a" relationship. By following the inheritance structure of the individual classes and their method resolution order (MRO), the graph can be expanded down to the very basic (abstract) base classes. For example, in our API, the "Volume" class inherits from the abstract base class "Quantity" (i.e., "Volume"-"is_a"-"Quantity"), and requires the two inputs -"value" and "unit" -in its constructor (i.e., "Volume"-"has_property"-"value" and "Volume"-"has_property"-"unit"). The value itself is of type float (i.e., "value"-"is_a"-"float"), the unit is of type string (i.e., "unit"-"is_a"-"string"). Ultimately, both floats and strings (as well as all other custom or built-in classes and types in Python) are "objects" (this relationship is excluded from the graph since it carries no added information in this context). Lastly, the fields have values associated with them represented by a "has_value" relationship (e.g., for a volume of 5 mL: "value"-"has_value"-"5" and "unit"-"has_value"-"mL"). This way, a knowledge graph can be constructed from the underlying ontology. Figure shows an example of a full knowledge graph as well as three example queries of this graph that were generated from the node graph shown in Figure in the supporting information.