1.  Field of the Invention
The present invention relates to a distribution system for distributing procedures (application programs etc) and/or data (jointly referred to as “contents”) to a plurality of clients such as clients present over a wide area and/or clients provided in mobile units.  In particular, it relates to a distribution system whereby efficient distribution can be performed which is adapted to dynamic changes in demand for the procedures or data, by utilizing distribution technology such as the Internet. 
2.  Description of the Related Art
Conventionally, distribution systems whereby procedures or data are distributed to a plurality of clients are utilized, for example, when product catalogues or inventory information etc are distributed to sales companies or small retailers worldwide, or when an information provider distributes programs or data for the provision of services to a large number of members, or when data such as map information or weather information or viewer programs for the data are distributed to vehicle-mounted/mobile information terminals. 
FIG.  19 is a layout diagram showing an example of a conventional distribution system.  A distribution server 1 (parent server) is a server constituting the distribution source for procedures and/or data, and a plurality of clients 3 constitute the distribution destinations of the procedures and/or data.  In this case, a single distribution server 1 distributes the requested procedures or data in response to requests from all the clients 3.  Such a distribution mode is frequently employed by an information provider when providing a distribution service for procedures or data using the Internet. 
FIG.  20 is a layout diagram illustrating another example of a prior art distribution system.  The distribution system shown in FIG.  20 attempts to disperse the load on the parent server 1 and the network connected to parent server 1 by dividing the distribution destinations for the procedures or data into a plurality of areas, and providing one or a plurality of child servers 2 for each area.  In this distribution mode, a client 3 is associated with a specific area, and receives distribution of procedures or data specific to this area from the child server 2 that is responsible for this area.  Also, procedures or data that are common to all areas are directly supplied from parent server 1.  Such distribution systems are utilized by information providers that distribute procedures or data on a world scale, and by enterprises having a large number of clients 3 on a national/world scale. 
However, with the conventional distribution system shown in FIG.  19, since, as described above, a single distribution server 1 performs distribution of procedures or data to all the clients 3, if there are a large number of simultaneous distribution requests, the load on the distribution server and/or network is increased, giving rise to a problem that in some cases a condition may be produced in which the server or network become unusable. 
Furthermore, in the case of the distribution system shown in FIG.  20, although, as mentioned above, this has a configuration whereby the load on the parent server 1 and the network connected to the parent server 1 is dispersed, when a large number of distribution requests to parent server 1 are generated simultaneously, in order to prevent this from resulting in a load concentration, on each occasion, it is necessary to perform an operation to change the distribution source from a parent server 1 to a child server 2 that is closest to the client 3.  Although, in order to render such an operation unnecessary, means may be adopted whereby the parent server 1 and all of the child servers 2 are provided with all of the procedures or data that are to be distributed, a problem results that storage equipment having a large capacity must be provided at each of the child servers 2, since even procedures or data in which the frequency of use (distribution requests) is extremely low have to be stored therein.