Design Issues
Support for a seamless access (security)
Support for distributed, heterogeneous Back-End services (HPCC, DBMS, Internet, ...) managed independently from Gateway
Variable pool of resources: support for discovery and dynamical incorporation into the system
Scalable, extensible, low-maintenance Middle Tier
Web-based, extensible, customizable, self-adjusting to varying capacities and capabilities of clients (humans, software and hardware) front end