A new web-based tool for data visualization in MDSplus

The Java tool jScope has been widely used for years to display acquired waveform in MDSplus. The choice of the Java programming language for its implementation has been successful for several reasons among which the fact that Java supports a multiplatform environment and it is well suited for graphics and the management of network communication. jScope can be used both as a local and remote application. In the latter case, data are acquired via TCP/IP communication using the mdsip protocol. Exporting data in this way however introduces several security problems due to the necessity of opening firewall holes for the user ports. For this reason, and also due to the fact that JavaScript is becoming a widely used language for web applications, a new tool written in JavaScript and called WebScope has been developed for the visualization of MDSplus data in web browsers. Data communication is now achieved via http protocol using Asynchronous JavaScript and XML (AJAX) technology. At the server side, data access is carried out by a Python module that interacts with the web server via Web Server Gateway Interface (WSGI). When a data item, described by an MDSplus expression, is requested by the web browser for visualization, it is returned as a binary message and then handled by callback JavaScript functions activated by the web browser. Scalable Vector Graphics (SVG) technology is used to handle graphics within the web browser and to carry out the same interactive data visualization provided by jScope. In addition to mouse events, touch events are supported to provide interactivity also on touch screens. In this way, waveforms can be displayed and manipulated on tablet and smartphone devices.