Abstract: The invention concerns a digital processing system fed by at least one filter having three possible states resulting from one or more conditions on one or more protocol attributes, specified for a semantic stream. Each protocol attribute is specified by an ordered sequence of protocol names used in the semantic stream and a parameter name carried by a protocol whereof the name is indicated in the ordered sequence of protocol names. The digital processing device comprises a filtering engine which applies the filter on the communication data until the data provide protocol attribute values wherefrom results a valid or invalid state of the filter and an action motor which triggers the action when the state of the filter is valid.