13. A computer program product comprising a computer readable storage medium having stored therein computer usable program code for operating a publish/subscribe message broker, the computer usable program code, which when executed by a computer hardware device, causes the computer hardware device to perform: receiving a message on a topic from a publisher; identifying the message as a start of a sequence of messages; transmitting the message to one or more existing subscribers to the topic; and transmitting in response to a new subscriber registering to the topic and a further message associated with the sequence being received on the topic from a publisher, the further message to the one or more existing subscribers to the topic, but not to the registered new subscriber to the topic.
13. A computer program product comprising a computer readable storage medium having stored therein computer usable program code for operating a publish/subscribe message broker, the computer usable program code, which when executed by a computer hardware device, causes the computer hardware device to perform: receiving a message on a topic from a publisher; identifying the message as a start of a sequence of messages; transmitting the message to one or more existing subscribers to the topic; and transmitting in response to a new subscriber registering to the topic and a further message associated with the sequence being received on the topic from a publisher, the further message to the one or more existing subscribers to the topic, but not to the registered new subscriber to the topic. 14. The computer program product according to claim 13 , wherein the message is identified as the start of the sequence of messages based upon content of the message.