An introduction to the URL programming interface

Create ubiquitous controlled access to devices using UPI

By Rinaldo Di Giorgio, JavaWorld.com, 09/20/99

Page 3 of 7

http://papercompany.plant5.building6.flr3.conveyor1/Status.html

Once you've read the status, you could use the following URL to change a conveyor belt's realtime routing:

http://papercompany.plant5.building6.flr3.conveyor1/Route?close=down&ope

Building such a system with Java will produce a software system that is more secure and easier to maintain than current approaches. If you instead chose to use typical current technologies, you would encounter a host of difficulties, including:

• Custom protocols
• Languages that have potential security flaws, such as direct access to the stack, private members using pointers, or no type safety
• Out-of-band facility for updating code
• No direct platform support for the Web and URL

The above problems have arisen in my real-life experiences developing just the sort of system under consideration. My goal was to allow remote corporate locations to participate more in the day-to-day operation of a plant. 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. Today, I could base a solution to this problem on UPI and a low-cost, off-the-shelf, single-board computer that runs Java or Embedded Java; forty such boards would have been all that was necessary, and this would cost less than 0,000 -- significantly less than the old multimillion dollar solution. 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. For example, it is not acceptable to have to reload a Web page in order to get accurate up-to-date data on it. Java solves this problem quite easily by allowing Web applications to have state.

Remote corporate locations

Corporations possess widely distributed enterprises and could benefit from being able to offer services -- energy control, maintenance, and alarm services, for example -- to remote locations. Integrating these services will reduce costs significantly. In 1979, while working for GTE, I installed the first networked electronic cash registers for McDonald's. These registers would call up corporate headquarters and report on daily transactions, and this information was used to schedule the shipping of product. Today, you can easily install a network in a store and query the store's various devices, including fryers, filters, thermostats, alarm and fire control systems, and so on. Corporations can reduce costs by centralizing administration. As with home automation, security is extremely important to remote corporate applications. If you have a thousand stores on the Internet, how do you control access easily?

UPI Interface to devices

Sun Labs has developed three prototypes that demonstrate how the UPI can be used to support the following specific devices. With a little imagination, this implementation can be abstracted to conveyor belts, sensors, and so on.