1. A method, comprising: causing storage of a set of subscriptions in a routing table of a first broker, causing sending of a set of messages from the first broker to a second broker according to at least one subscription stored in the routing table, receiving a subsequent message, determining a search term based on a data element of the subsequent message, comparing the search term with a set of data elements stored in an operational memory of a repository, controlling sending of the subsequent message to the second broker according to a result of said comparison, wherein the set of data elements stored in the operational memory of the repository comprises data elements of the messages previously sent to the second broker, and wherein said set of subscriptions contains at least one subscription, which specifies a topic, which is not contained in the set of data elements stored in the operational memory of the repository, and adding a new data point to the operational memory of the repository when the subsequent message has been subscribed by at least one subscriber and no matching data elements are found in the operational memory of the repository.