The GAF ontology defines two relations:

• gaf:denotedBy relates an instance to a mention of this instance
• gaf:denotes relates a mention to the instance it refers to

The following classes are defined:

• Instances: a general class of any kind of entities (including events, locations, people, etc., even a mention can be included in this class)
• Mentions: members of this class refer to some entity

The GAF ontology can be found here.