Facts either consist of a particular item or a relation between items. To this query, Prolog will answer yes. Prolog matches it in its database of facts.
Facts have some simple rules of syntax.
Facts should always begin with a lowercase letter and end with a full stop. Examples of Simple Facts Here are some simple facts about an imaginary world. These describe a particular set of circumstances for some character john. We can interrogate this database of facts, by again posing a query. The first two queries succeed since they can be matched against facts in the database above.