Key aspects of a JViews Diagrammer user interface

Symbols are the starting point of a display (diagram or dashboard). A symbol is a self-contained graphic object that represents a physical or conceptual element in the underlying application. For example, symbols can represent trucks, factories, network elements, dials or gauges. They have built in behavior which means that they react dynamically to data changes or user interaction.

A symbol and its behavior are not defined by code but in a CSS (Cascading Style Sheet) file that contains a description of the JavaBeans™ to use, their settings and logic. At run time, a generic engine instantiates the right class and configures the created instances as specified in the CSS file. For better performance, or if such symbols can be frozen for a given application, it is also possible to generate Java™ source code corresponding to these symbols.

Applications that must automatically create a diagram from a data source (like workflows, business processes, entity relationships, or network topologies) use a model-driven approach. The design tool used to create this type of display is the Designer for JViews Diagrammer. The Designer creates a display by binding the data source elements to symbols created with the Symbol Editor. For example, you can specify that a given type of data instance be represented by a given symbol, and that a particular value of a field be bound to some symbol parameters to alter the aspect of the symbol. The specification of how the visual aspect of the symbol is controlled by the data model is performed at a high level as the symbols already contain their particular visual logic. Other aspects of the display, such as automatic graph layout options, links, background images, subgraphs, zooming can also be tuned through the Designer tool. The mapping between the data model and the visual entities (symbols) is described in a CSS format. The output is a project file combining the CSS part and the XML part (data source) and can be loaded into the application at run time. The project’s individual elements can be accessed through dedicated Java classes for further customization of the look or behavior of the display.

To build displays for monitoring or supervision purposes (like industrial schematics, business dashboards, and other generic human-machine interfaces), the approach is quite the opposite from the model-driven approach, in the sense that you start by manually placing symbols created with the Symbol Editor on top of a static background. This is done with another design tool called the Dashboard Editor. Symbol parameters can be associated with application data at design time, but this mapping will be resolved only at run time when connecting the actual data source. The resulting dashboard or schematic is an XML file associated with palettes of symbols that can be loaded into an application window and fed with real-time data.