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Remote Monitoring

We would like to use our zones to monitor temperature data. We will have to assume these temperature readings have already been connected to a server using a messaging technology such as XML-RPC (XML-Remote Procedure Calls), JMS (Java Messaging Service), or even SOAP (Simple Object Access Protocol). Exploring these messaging options is outside the scope of this project. In this project, we look only into the SVG aspects of monitoring a live data stream, regardless of how the data is received at the server. The approach we will use takes advantage of a couple of extensions to the SVG specification, getURL() and postURL(). They are Adobe SVG Viewer–specific extensions that will not necessarily be available to other viewers.

Here is a brief overview of the monitoring process. First, the user selects a zone with a mouse click, which calls the ECMAScript click function to open a new window. This window is opened with an image/svg+xml stream from a servlet that creates a temperature cylinder graph and control panel. The graph is actuated with a start button in the control panel, which calls the dataUpdate function found in the associated ECMAScript file, graph.js. dataUpdate is a recursive function set up in a timer that uses getURL(servlet_URL, call_back) to get a temperature response from our servlet. The servlet collects the next available temperature data and sends back this information in the status object of the call_back function. When this temperature data is available to the ECMAScript, a new line segment, label, and point are inserted in the SVG graph.


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