The SubPos Standard defines the method in which to encode positioning data into a Wi-Fi beacon frame by means of structuring the SSID of the frame such that it is compatible with the majority of existing Wi-Fi hardware. As such the standard consists of the following:
Path Loss Calculation - Optional
Extensibility - Optional
Through this information you can determine your position through various means of trilateration and averaging. The Nodes and Android API implement this functionality, but the standard doesn't mandate this.