Ontology

 

We follow Quine in taking the ontology of a system to be given by the collection of domains over which variables range. In the supermarket example, the ontology includes

products

These can be represented by their product codes.

purchased items

The particular instances of items purchased as part of a particular basket.

baskets

The collection of items purchased on a particular occasion.

customers

The set of customers is unknown but is known to exist

characteristics of products

durable, edible, assumes a dog

characteristics of people

female, married, has baby, has toddler, Hispanic tastes

There's lots more in the ontology.