The outermost layer of the hub receives requests from client applications on the network to either store or retrieve data. In our present system, these requests must be composed using a standard message syntax called Health Level 7 (HL7). (Other messaging protocols could be supported by this layer if they were required.) This architecture enables applications on a variety of platforms (DOS, OS/2, UNIX) to communicate with CIS services. Messages are queued, verified, logged, and ultimately passed to the inner layers of the hub. Data submitted by client applications will ultimately be stored in the central Repository. Data requested by a client application will be retrieved (by inner layers of the hub), and returned to the client system.
For example, laboratory data is being sent to the hub (dotted line going toward center). After this transaction takes place, the outpatient application can retrieve this data from the central hub (dotted lines going toward outpatient box).