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TANDBERG Gatekeeper/Border Controller API User Guide
D14172.01 page 8 of 84
1.3 The TANDBERG XML Engine
The TANDBERG XML engine is optimized for advanced machine-machine interaction between a
TANDBERG system and an external control application. The main features can be summarized as:
• Structuring of information
• Addressing using XPath
• Feedback
1.3.1 Structuring of Information
An application programming interface can be seen as a gate where information is exchanged between
two systems: a control application and a target system. The control application transmits instructions
to the target system, while the target system supplies information about how these instructions are
executed, in addition to other system related information.
Thus, the exchange of information can be divided into:
1. information flowing from target, hereby called read information (r)
2. information flowing to target, hereby called write information (w)
If we now look at the TANDBERG systems we can identify three main types of information, either
being read information (r), write information (w) or read-write information (rw):
1. (r) Read information – Status Information.
Information about the system and system processes, i.e. information generated by the system.
For example: status about registered systems, ongoing calls, network status etc.
All status information is structured in a hierarchy, making up a database constantly being
updated by the system to reflect process changes.
2. (w) Write information – Command Information.
Information supplied by the user to initiate an action.
For example: instructing the system to place a call, disconnect an existing call, remove a
registration etc.
A command is usually followed by a set of parameters to specify how the given action is to be
executed.
3. (rw) Read-Write information – Configuration Information. Information defining system
settings. This information can both be supplied and read by the user. For example: IP settings,
bandwidth settings, enabling/disabling of various features etc.
All configuration information is structured in a hierarchy making up a database of system
settings. But for the Configuration information, the data in the database can only be updated by
the user/control application.
1.3.2 Addressing using XPath
To address information in the hierarchic structure of Status and Configuration information the
TANDBERG systems support abbreviated XML Path Language (XPath). This allows the user/control
application to address everything from a single element of data (for example the source address of a
specific call), to larger parts of the hierarchy (for example all information available for a given call).
The structuring of information together with XPath for addressing makes up powerful features like
searching and setting of multiple instances of a configuration.
1.3.3 Feedback
Feedback is an extremely powerful feature where the TANDBERG system actively returns updated
status and configuration information to the user/control application whenever changes occur. The
user/control application can specify what parts of the status and configuration hierarchies it wants to