Grounding Geographic Categories in the Meaningful Environment

Ontologies are a common approach to improve semantic interoperability by explicitly specifying the vocabulary used by a particular information community. Complex expressions are de ned in terms of primitive ones. This shifts the problem of semantic interoperability to the problem of how to ground primitive symbols. One approach are semantic datums, which determine reproducible mappings (measurement scales) from observable structures to symbols. Measurement theory o ers a formal basis for such mappings. From an ontological point of view, this leaves two important questions unanswered. Which qualities provide semantic datums? How are these qualities related to the primitive entities in our ontology? Based on a scenario from hydrology, we rst argue that human or technical sensors implement semantic datums, and secondly that primitive symbols are de nable from the meaningful environment, a formalized quality space established through such sensors.