A first database and a second database have different schemas. An activity in a workflow accesses a data item in a list by invoking a method in an interface of a list object. The list comprises a collection of data items. Each data item in the list comprises an item key field specifying an item key. No two data items in the data item collection have item key fields specifying a shared item key. In addition, each data item in the list comprises a set of additional fields. Each field in the set of additional fields has a value derived from the first database or each field in the set of additional fields has a value derived from the second database. In this way, the activity can be implemented without knowledge of the different schemas of the first database and the second database.