Task: Class Definition Understanding (ontology: Legal/LKIF_Core_Ontology)

Which of the following definitions best describes 'Occurrence'?

A. An occurrence in space-time
B. Metaphor of physical concepts, i.e. the things we mentally manipulate, either in thought or memory
C. The physical world evolves around two main classes: physical objects and processes.

In lkif-core, the physical world evolves around two main classes: physical objects and processes. Objects are pieces of matter, while matter is typed by substances. Objects have mass, extension, viz. form and aggregation state (which limits form). Objects are the specification of the notion that matter, and in particular solid objects, is what makes the physical world relatively stable and observable. We define (physical) situations in the first place by the arrangement of physical objects (entities).
D. A consequence of our clear separation of ontology from models of situations (occurrences), is well exemplified in the two ways we look at time and space. Things happen against the canvas of space and time. This 3D canvas moving in time (or whatever metaphor) allows us to index instances of objects and processes. Time and space provide positions in time and space for objects. Positions are in general modeled in some mereological framework. However, the objects and processes as classes have time and space properties in a different way. Space occupied by an object is its inherent property of size or extension. This property was for Descartes even the critical one that separated mental (not: abstract) objects from physical ones. Processes occupy (consume) time; they take some duration. This time resource is inversely related to the consumption of energy. This distinction between position and extension is also made in various other ontologies. However, this distinction is easily obscured by the fact that the extension of an object can also be used as a reference for location. An object can be in another object. In fact, any physical object can be used as a spatial and even temporal referent. This does not refute our view that locations are occurrences. To be precise: extension is an inherent, necessary property of a physical object or process; its location is an accidental one.

Answer: A consequence of our clear separation of ontology from models of situations (occurrences), is well exemplified in the two ways we look at time and space. Things happen against the canvas of space and time. This 3D canvas moving in time (or whatever metaphor) allows us to index instances of objects and processes. Time and space provide positions in time and space for objects. Positions are in general modeled in some mereological framework. However, the objects and processes as classes have time and space properties in a different way. Space occupied by an object is its inherent property of size or extension. This property was for Descartes even the critical one that separated mental (not: abstract) objects from physical ones. Processes occupy (consume) time; they take some duration. This time resource is inversely related to the consumption of energy. This distinction between position and extension is also made in various other ontologies. However, this distinction is easily obscured by the fact that the extension of an object can also be used as a reference for location. An object can be in another object. In fact, any physical object can be used as a spatial and even temporal referent. This does not refute our view that locations are occurrences. To be precise: extension is an inherent, necessary property of a physical object or process; its location is an accidental one.