In 2003 the Swedish Defence Research Agency (FOI) started to consolidate work within the simulation domain to use the same simulation framework where applicable. To meet this end, that is, a distributed simulation architecture, the high level architecture (HLA) was selected to ease collaboration between research projects.
It soon became clear that a scenario editor and scenario engine were needed to manage distributed simulations. Existing products filling this need, at the time, were either too expensive or not flexible enough for the purpose; a scenario tool needed to be developed.
One requirement for the scenario tool was to use as few licensed software packages as possible and to be able to run on UNIX, Linux, and Windows. For many reasons, Java was the obvious choice to develop this scenario tool.
Another requirement for the scenario tool was to have the whole scenario of a simulation in one central location. That includes setup of participating applications in a distributed simulation and which applications should participate.
One of the software engineers in the project, Mikael Brännström, had done previous work on a demo using the NetBeans Platform and the decision was made to use the NetBeans Platform as the base for the scenario tool.
The central component for a simulation is, of course, the scenario. The type of content in a scenario is described in a scenario model. Both scenario and scenario model can be represented in XML.
Below is a representation (click to enlarge it) of a scenario and the simulation-related classes:
- The Scenario contains the main components of the simulation, entities, paths and coverage diagrams. These objects are persistent and are editable in NetScene.
- An Entity describes a physical or an abstract part in the simulation, for example a vehicle or a part of a software system. An Entity has a set of attributes, for example position or color. It also contains parameters that describe the relation to the parent, or container, of the entity, for example the relative position and orientation of a camera entity to the human that are carrying the camera. An Entity can have an EntityModel that performs some behavior of the entity.
- An EntityModel is executed by the SimulationEngine during the simulation and it has full access to the rest of the scenario. An EntityModel can model behavior of the entity, such as motion or sending Messages.
- A Message is an object used to handle communications between entity models and/or plug-ins, for example a sensor track or
- A Path contains a number of waypoints. A Path can be used by for example a motion model. Different interpolations can be selected for a path.
- A CoverageDiagram is used by for example sensor coverage.
The scenario model is the scenario palette that hierarchically describes the components which can be used to create a scenario.
The scenario model describes:
data types: simple or complex
entity classes: class hierarchy, attributes, relations between entities and default values
message classes: parameters
coverage diagram classes: parameters
- The top left window contains a representation of the current scenario. It contains all entities, paths and coverage diagrams of the scenario. It also contains those scenarios that are included from the current scenario.
- The top right window contains scenarios and game configurations. These nodes are identified from the project files with MIME-resolvers. From this window scenarios can be merged or included to the current scenario. A merged scenario simply adds content to the current scenario. An included scenario acts as a reference to the included scenario, enabling several scenarios to be edited in the same context.
- The bottom left window contains a representation of the current scenario model. Entities and entity models can be dragged and dropped from this window to the middle window to create new entities or to add entity models to existing entities.
- The bottom right window contains a customizable properties window that can be configured by the user. It also differs from the normal property view in the way that it contains tools for the user to quickly manipulate complex types of the selected node.
- The middle window contains a map of the current scenario. Several maps can be open at the same time. Maps can be geo-referenced images, WMS maps and 3D maps. These windows also supply several tools for editing the scenario spatially.
In part 2, you will read about concept development & experimentation with NetScene, as well as NetScene's plugins, and the applicability of these developments to multi-sensor systems.