An incidence correspondence I is a correspondence from an AbstractVariety X (the source of I) to another AbstractVariety Y (the target of I) which is mediated by a third AbstractVariety Z, together with AbstractVarietyMaps f:Z→X and g:Z→Y.
Given a cycle x on X, the pushforward of x along I is
and similarly for bundles on X. Likewise, if y is a cycle on Y, the pullback of y along I is
and similarly for bundles on Y. See Correspondence ^* and Correspondence _* for more info.
The tuple (Z,f,g) can be accessed via the intermediates command.
The object IncidenceCorrespondence is a type, with ancestor classes Correspondence < MutableHashTable < HashTable < Thing.