Equivalence Classes are an important concept used throughout the compiler.

Set operations are used to manipulate objects and their classes. Some common operations include:

• without-<class> remove information
• with-<class> add information (strong)
• guess-<class> add information (weak)
• with-only-<class> add & normalize information (strong)
• guess-only-<class> add & normalize information (weak)
• has-<class> query whether information is present (strong)
• is-<class> query whether conjugate satisfies a predicate (strong)

Some common type classes include:

• representation
• size
• fields
• datatype-normal
• datatype-tag
• property
• proposition

Type Slots are similar to classes but are much more specific. A Slot is a single Ground Type possibly with some parameters but nothing else.

• with-slot add information
• with-only-slot narrow information
• without-slot remove information

A type is said to be normalized when it contains only the minimal amount of information to uniquely identify itself.

A type is said to be denormalized when it contains the maximum amount of information that can be strongly inferred from its normal form.