Towards a semantic model for Java wildcards
Alexander J. Summers, Nicholas R. Cameron, Mariangiola Dezani-Ciancaglini, Sophia Drossopoulou · 2010
Wildcard types enrich the types expressible in Java, and extend the set of typeable Java programs. Syntactic models and proofs of soundness for type systems related to Java wildcards have been suggested in the past, however, the semantics of wildcards has not yet been studied.