ConceptSubtyping relationModified just nowProperties 3Hide BooksChapter 5. Types JourneyProgramming Language Theory StatuslearningWritten X<:YX <: YX<:Y, a formal ordering on types meaning "XXX is a Subtype of YYY" - XXX substitutes for YYY.Written X<:YX <: YX<:Y, a formal ordering on types meaning "XXX is a Subtype of YYY" - XXX substitutes for YYY. Previous in ConceptsSubtypingNext in Concepts Sum of products sop