A feature control frame will have a segment count.

An FCF will have a tolerance type.

An FCF will have a tolerance value.

An FCF will have 0 - 3 datum references.

A tolerance value may have a zone shape.

A tolerance value may have a material modifier.

A tolerance value may have a unilateral specification.

A tolerance value may have a projected designation and length.

A datum reference may be a compound datum.

A datum reference may have a material modifier.

A datum reference may have a controlled direction specification.

A datum reference may allow translation.

A composite tolerance has rules about datum reference subsets.

A composite tolerance has rules about tolerance values for successive subsets.