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 allocate to the received transaction a local source identity information as source identity information, the local source identity information comprising one of a set of reusable local source identity information. This ensures the order of transactions tagged with a same original source identity and target and allows transactions tagged with different source identifiers to be processed out of order.