The observation pattern represents one of the most common and widespread coordination schemata in today complex models and systems, as it emerges from a variety of different research and application areas. This paper aims first at providing a common ontological foundation for the many different models, architectures, and systems supporting the observation pattern, allowing them to be classified and compared despite their seeming diversity. Based on such an ontology, this paper introduces then a coordination framework to formally model the observable behaviour (manifestation) of a knowledge source, as well as its interaction with observers. The expressiveness and effectiveness of both the ontology and the coordination framework are put to test by expressing manifestation and observation as they occur within both well-known coordination models and different paradigms like object-oriented languages, active databases, and agent systems.