Before using the Vision2 API you will need to generate a session ID. The session ID is a GUID (in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx) which can be generated using any of the following websites
Or by using a downloadable file obtained from http://guid.codeplex.com/releases/ API using a unique username
You must also generate a unique username and ensure that you use the same username and guid together at all times. You will need to keep the session alive by calling the V2Master_KeepAlive command with the username and sessionID as parameters every 5 minutes. This mechanism is used to lock a service to your API so no other users in the system can interfere with the service you are modifying until you have finished."