1. A system for filtering messages between subscribers to a message channel, comprising: a message broker component adapted to allow subscribers to publish messages to a message channel; a message filter on each subscriber, each message filter containing a filter value for at least one subscriber on the message channel; and a query component on each subscriber, each query component adapted to extract data from a message to be published, whereby the extracted data can be compared with the filter value in order to determine whether a subscriber should receive the message.