Programming Language Theory ConceptSubtyping relationProperties 3Hide BooksChapter 5. Types JourneyProgramming Language Theory StatuslearningWritten X<:Y, a formal ordering on types meaning "X is a Subtype of Y" - X substitutes for Y.Written X<:Y, a formal ordering on types meaning "X is a Subtype of Y" - X substitutes for Y. Previous in ConceptsSubtypingNext in Concepts Sum of products (SoP)