OptionalcolorSource node of this edge
OptionalfromStores the equivalence class if the edge is based on a relation that has one as a source or if this edge is derived from an equivalence class itself.
Target node of this edge
OptionaltoStores the equivalence class if the edge is based on a relation that has one as a target or if this edge is derived from an equivalence class itself.
An edge in an argument map derived from an [[IRelation]] or an [[IEquivalenceClass]].