Data Types

Each data entry specifies a datatype from the following set (from Franca IDL). Datatypes shall not be used in branch entry

Supported datatypes

Name Type Min Max
uint8 unsigned 8-bit integer 0 255
int8 signed 8-bit integer -128 127
uint16 unsigned 16-bit integer 0 65535
int16 signed 16-bit integer -32768 32767
uint32 unsigned 32-bit integer 0 4294967295
int32 signed 32-bit integer -2147483648 2147483647
uint64 unsigned 64-bit integer 0 2^64 - 1
int64 signed 64-bit integer -2^63 2^63 - 1
boolean boolean value 0/false 1/true
float floating point number -3.4e -38 3.4e 38
double double precision floating point number -1.7e -300 1.7e 300
string character string n/a n/a


Besides the datatypes described above, VSS supports as well the concept of arrays, as a collection of elements based on the data entry definition, wherein it’s specified. By default the size of the array is undefined. By the optional keyword arraysize the size of the array can be specified. The following syntax shall be used to declare an array:

# Array of datatype uint32, by default size of the array is undefined
datatype: uint32[]
# Optional: specified number of elements in the array
arraysize: 5

An example for the usage of arrays is Vehicle.OBD.DTCList which contains a list of Diagnostic Trouble Codes (DTCs) present in a vehicle.


Timestamps are in VSS typically represented as strings, formatted according to ISO 8601. Timestamps shall be expressed in UTC (Coordinated Universal Time), with special UTC designator (“Z”). Time resolution SHALL at least be seconds, with subsecond resolution as an optional degree of precision when desired. The time and date format shall be as shown below, where the sub-second data and delimiter is optional.


Data Streams

Data Entries, which describe sensors offering binary streams (e.g. cameras), are not supported directly by VSS with a dedicated data type. Instead, they are described through the meta data about the sensor itself and how to retrieve the corresponding data stream.

A camera can be a good example of it. The Data Entry for the camera and the corresponding video stream could look like:

  type: branch
  description: Information about the camera and how to connect to the video stream

  type: actuator
  datatype: boolean
  description: If the camera is active, the client is able to retrieve the video stream

  type: sensor
  datatype: string
  description: URI for retrieving the video stream, with information on how to access the stream (e.g. protocol,  data format, encoding, etc.)

In this example, it shows the usage of meta data about the status of the sensor. The camera can be set to active through the same data entry (actuator). A dynamic data entry (sensor) is used for the URI of the video stream. Information on how to access the stream is expected.