An ARIS assignment is a feature to navigate from an object occurrence such as an ArchiMate® element to a model. This model could be specified in another modeling language such as UML, BPMN, etc. This way an ArchiMate® user can drill down from an architecture landscape model directly into a design specification model.
Assignments can be used to navigate from a coarse-grained ArchiMate® element, for example, a business process, to a detailed specification model for that element, for example, a BPMN collaboration diagram.