1. An event delivery apparatus for delivering, on network, an event comprising data and semantic information, being metadata of the data, based on the semantic information, said event delivery apparatus comprising: an event place that is a place for comparing an event sent from an event sender with a filter in which semantic information of an event that one or more of a plurality of event receivers with to receive is registered as an event acquisition condition, said plurality of said event receivers being different from said event sender, said event place being the smallest unit in which semantic information is described based on a common ontology system, to limit an event delivery range, said event place including, distinct from said event sender: a plurality of semantic information switches each of which compares semantic information assigned to said event sent from said event sender with semantic information registered in said filter and delivers said event sent from said event sender to said one or more of said event receivers registered in said filter among said plurality of said event receivers when said semantic information of said event sent from said event sender is coincident with said semantic information of said event registered in said filter; and a semantic information router connected to said semantic information switches to route said event between said semantic information switches based on said semantic information, and forwards said event between said semantic information switches; wherein said event place is provided with: a central processing unit; and memory connected controllably by said central processing unit, and said memory stores software that can be executed in said central processing unit, which creates a shared link for forwarding an event based on physical link information of an event place object that achieves said semantic information switch, and which, based on a shared link established by a shared link object, routes an event between said semantic information switches, and forwards an event between said semantic information switches, and said event place achieves said semantic information router by executing said software; said central processing unit executes said program, which when forwarding an event between said semantic information switches, establishes an event path for each event type by registering a filter for delivering said event to a series of event place objects, and in which two latest identifiers of event place objects that it has passed through are held as control information for an event to be forwarded, so that infinite event forwarding is prevented by reference to said control information; and when delivering an event, said semantic information router is provided with: an event identifier assignment function for assigning each event an identifier that can identify it uniquely; and a detection function for detecting whether a duplicate event was delivered from a different path by comparison with event identifiers that were delivered and stored in the past.