In addition to an OPC client (OPC Driver), E3 also works as an OPC Server DA (Data Access) 2.0x. This allows E3 to expose all existing objects in the executing Domain (I/O Tags, for example) to applications external to E3. Some examples are Elipse SCADA, E3, which can be executing on another application as a client, or an OPC client from another manufacturer, as long as this client implements the OPC DA 2.0x standard or later.