Fortunately, open middleware is available to address the needs of both thin clients and the traditional (thick) client. The thin client version of the middleware works in conjunction with a server (Figure 4-b), which provides a remote execution environment for the POS application. The middleware can simultaneously support many clients by running a separate instance of the POS application software for each attached device. Or if preferred, the 4690 controller itself can act as the POS thin client server (Figure 4-c). Thin client solutions are of particular interest to retailers implementing mobile solutions or who simply want to reduce the total cost of ownership by using less expensive POS devices. A number of retailers are actually using this same thin client solution to "upgrade" and prolong the life of old IBM POS devices that don't have the capacity to run newer (bigger) versions of the POS applications.