DERIVING OVERLAY INFORMATION FROM A USER INPUT FOR A BASE MESSAGE SCHEMA ASSOCIATED WITH A NODE IN A MESSAGE FLOW

There is disclosed a method, apparatus and computer program for deriving overlay information from a user input for a base message schema associated with a node in a message flow. The base message schema is presented to the user and has at least one variable portion. A user selection of a variable portion of the base schema is received. The user is then provided with possible overlay schema information for the selected variable portion. A user selection of the schema to be overlaid on the selected variable portion is received. The selected overlay schema is associated with the base schema.