6/123.4.5 Hyperwave Gateways
Hyperwave provides both front-end (client) gateways and back-end (server) gateways. Back-end gateways allow for transparent access to data which is not stored on the Hyperwave server but on external databases or servers. To realise the gateway one can either use CGI programs (Common Gate Interface; see Section 3.3.7) or Hyperwave's HGI (Hyper-G Gateway Interface). CGI programs have a drawback in that for each request the program is executed and terminates as soon as the request is finished. With HGI you are able to write gateway programs which allow persistent connections to external databases. The SQL-gateway, for instance, allows an author to create remote Hyperwave objects which dynamically retrieve information from an external database via a SQL interface. The retrieved data is transparently integrated into the Hyperwave collection hierarchy. This allows users to navigate in a consistent manner even through external databases.
The back-end WWW-gateway allows for the insertion of remote objects which retrieve documents from a WWW server. In the same way gateways to Gopher, WAIS, FTP, and even Telnet are feasible.
On the other hand, Hyperwave provides client gateways which allow for WWW clients, Gopher clients, or network managements clients (SNMP) to access Hyperwave. Because of the very high distribution of WWW clients like Netscape Navigator or Microsoft Internet Explorer, access through the WWW gateway (WaveMaster) has become the most important. End-users are no longer forced to install native Hyperwave clients to browse and modify documents on a Hyperwave server.