A package includes a die and at least one further die. The die has an interface configured to receive a transaction request from the further die via an interconnect and to transmit a response to the transaction request to said further die via the interconnect. The die also has mapping circuitry which is configured to receive the transaction request including at least first source identity information, wherein the first source identity information is associated with a source of the transaction request on the further die. The mapping circuitry is configured to modify the transaction request to replace the first source identity information with local source identity information, wherein that local source identity information is associated with the mapping circuitry. The mapping circuitry is configured to modify the received transaction request to provide said first source identity information in a further field.