Virtually every plant in the world has its own set of unique protocols for communicating with devices, which adds to cost and complexity. If I were designing a new factory, I would use a Web-based architecture that requires that all devices communicate via Jini or HTTP protocols on the main interconnection network, and support all of the legacy devices with proxy services that convert the specific device protocols into a URL protocol. The above problems have arisen in my real-life experiences developing just the sort of system under consideration. I spent several years creating applications for the pulp and paper industry, and in this particular project we developed a packet-switched network that cost several million dollars. It let users view the status of the paper winders and calendaring machines in plants distributed throughout the world.
Winders roll up the paper, and calendars make the paper surface glossy.
We will discuss this in more detail later. One of the challenges and areas requiring further interface is the lack of state on the Web. Java solves this problem quite easily by allowing Web applications to have state.