Emotion, or mental feelings, can be experienced in various degrees of intensity. An attribute of feeling is some particular “relative amount” of happiness, confidence, fear, or whatever. These “relative amounts” can be measured and described with terms such as “low amount of”, “very high amount of”, etc. For example, Cyc can deal with the attribute of feeling a relatively low amount of happiness. (Note that Happiness itself is not an individual feeling attribute but type of feeling — instances of which are the individual attributes of feeling particular relative amounts of happiness; a low amount of happiness is one such instance. Feeling types organize into a lattice; for example, there are several more specialized forms of happiness that are present in Cyc’s ontology, such as Elation, Delight, Triumph-TheFeeling, etc.
Perception in Cyc is an event in which an agent (a perceptual agent) acquires information through the exercise of its senses. Examples include reading, tasting something and listening to music.
Belief. Saying that an agent believes a given proposition means that the agent subscribes to the truth of the proposition. Note that the proposition might or might not actually be true. We can also talk about “belief statements” of a particular belief system. Each belief system is an ideology (systems of belief) in terms of which an agent characterizes (i.e., makes sense of) the world. Some belief systems are: Vegetarian Beliefs, German Nazi Ideology, Republican Party Ideology, Communist Ideology, Pacifist Ideology, and Atheism.