OSI contains an object-based environment description using the message format of the Protocol Buffer library developed and maintained by Google.
OSI defines top-level messages that are used to exchange data between separate models.
Top-level messages define the GroundTruth interface, the SensorData interface and, since OSI version 3.0.0, the SensorView, SensorViewConfiguration and FeatureData interfaces.
The following figure shows the interfaces and models involved in modeling a sensor.
OSI also defines interfaces for traffic participant models. These interfaces allow to send commands to traffic participant models and to receive their updated state. The following figure shows the interfaces of a generic traffic participant.
Traffic participant models may use other OSI interfaces internally, for example, to model autonomous vehicles. The following figure shows a more advanced use case for traffic participants.
OSI currently provides only limited support for data structures describing measured internal states of the traffic participant. Actuator intentions are currently not covered by OSI and must be handled with a different data description format.
All fields in an interface are set to optional and required is not used. This has been done to allow backward compatible changes in the field. Additionally, this is the default behavior in protobuf version 3 that does no longer have the required type and therefore ensures update compatibility. However, this does not mean that filling the field is optional. For the purpose of providing a complete interface, all existing fields should be set, unless not setting a field carries a specific meaning as indicated in the accompanying comment.
All field numbers of 10000 and upward are available for user-specific extensions via custom fields. Therefore, no future evolution of OSI will use field numbers of 10000 or above.