OpenSensorHub Toolkit

# General

The DataSource is the entry point defining some properties about the kind of data you want to display and how to connect to it.

There are properties to control the playback stream, server version, protocols, buffering, and some other network options.

osh-js comes with built-in datasource types:

# Data parsing

The second role of the DataSource is to provide a way to parse the data depending on the kind of DataSource we invoke. Each DataSource provides an inner parser which defines how to parse the data.

The DataSource uses a DataConnector which instantiates a WebSocket or HTTP connection to get results from the server. In case of GetResult request, it is preferable to use a WebSocket because it will keep a persistent connection between the client and the server.

For the case of using a WebSocket connector, the data is in the form of an arrayBuffer as defined into the WebSocket Specification (opens new window).

The DataSource parses the binary array to read the original content such as Text, Json, other binary data(video frames) etc.

Several types of DataSource exist. For the moment, they are divided into TimeSeriesDataSource and DataSource.

TimeSeriesDataSource inherits directly from DataSource and adds the notion of time. Indeed, it mainly concerns the GetResult request.

# Data after parsing

The data are mapped into internal Object. Each DataSource defines the properties of this object but some are common to every DataSource.

For the time being, two kind of message are supported: message and data.

# DataSource

# Common properties

Some properties are common to all DataSources. These are the DataSourceId, and the message type.

{
  type: "message",
  dataSourceId: "123-456-4569-4545"
}

# Data type message

The data type message are useful to send some message from the DataSource to the endpoint. For example, if the connector disconnects, then the dataSources can alert the view that the status of the connection has been changed.

The structure of such a message is:

{
  type: "message",
  dataSourceId: "123-456-4569-4545",
  status: Status.DISCONNECTED
}

# Data type data

These are the data messages. These objects are the result of parsing the source object received by the server to the internal object of the Toolkit. Each message contains a set of values, which in turn contains a timeStamp and an associated data.

The choice to pass an array rather than a single object is due to the fact that the batch property of the DataSource can be used. This property allows to receive a group of data rather than a single data item(see batch section). For example, if you want to display a Graph, it is often preferable to initialize it with all the data at once (for archive data) rather than updating it data by data.

The structure of such a message is:

{
    type: "data",
    dataSourceId: "123-456-4569-4545",
    values: [{
      data: {
        lat: 45.2,
        lon: 45
      }
   }]
}

# Global configuration

There are global properties common to every datasource owned by the DataSource Object.

API Reference

The customUrlParams are properties that are automatically appended to the URL as they are provided.

Example:


const dataSource = {
    ...,
    customUrlParams: {
        'someParams': 'value1'
    }   
};

This will give the following result URL:

http://some-url?..&customUrlParams=value1

The batchSize property allows to receive a group of data rather than a single data item. For example, if you want to display a Graph, it is often preferable to initialize it with all the data at once (for archive data) rather than updating it data by data. see batch section

The reconnectTimeout allows you to set the time before the connector tries to reconnect after being disconnected.

# Properties configuration

The general datasource properties allows to define the parameters of the data you want to fetch. Moreover, it is possible de get more control on the reconnection process and/or the synchronization algorithm when it is associated with a DataSynchronizer.

batchsize is useful if you want to process data in batches and display them all at once rather than displaying them one by one. For example, in the case of static data that one would like to display in a block.

To create a new datasource type, see the developer docs.

# TimeSeriesDataSource

This datasource allows to request the server with the notion of time. The temporal synchronization of the data is then possible for all DataSources inheriting it.

After the parsing, the data can be synchronized using the DataSynchronizer or/and displayed into a View.

# Data type data

The structure is similar to a DataSource but with a `timestamp' field allowing to add temporality to the data.

The structure of such a message is:

{
    type: "data",
    dataSourceId: "123-456-4569-4545",
    values: [{
      timeStamp: 1231545456,
      data: {
        lat: 45.2,
        lon: 45
      }
   }]
}

# Global configuration

There are global properties common to every datasource owned by the TimeSeriesDataSource Object.

API Reference

Example:


const timeSeriesDataSource = {
    ...,
    timeShift: {
        'someParams': 'value1'
    },
    timeOut: 100,
    bufferingTime: 100,
    replaySpeed: 1.5
};

The timeOut and bufferingTime are useful only for data synchronization.

The replaySpeed property allows to modify the same frequency of reception of archive data compared to their original frequency.

# Properties configuration

The general datasource properties allows to define the parameters of the data you want to fetch. Moreover, it is possible de get more control on the reconnection process and/or the synchronization algorithm when it is associated with a DataSynchronizer.

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