An XML Definition is a ruleset (defined through XML syntax) specifying a particular behavior. All of these rules and behaviors are Snom specific and do not apply to any other vendor.
XML Definitions allow the user to create keys that are fully customized based on their specific needs. For example a user can customize key LEDs colors and behavior, actions taken during a key pressure (and the key release too), and instruct the phone to subscribe to a SIP resource and then parse the XML body received into the in-dialog NOTIFY. The XML definition can setup various states and the phone can react to state changes and/or take action in different states.
It is also possible to create keys that change settings, dial numbers, send DTMF, launch a URL, request a certain module on the phone, etc.
An XML Definition can also be referred to as XML entity or XML description.
Standard XML Definitions are attached to a phone key. These can apply to any phone key except audio & number keys.
Some keys have obvious limitations, for example there is no LED on Context-Sensitive or Dedicated Keys.
The XML Definitions Tutorial shows how to configure and use standard XML Definitions.
General purpose XML Descriptions are XML Definitions that are not attached to a phone key. Instead, these are written inside general_purpose_xml_descriptions settings. The XML Definitions Tutorial contains details and examples regarding this feature.
General purpose XML Descriptions can be accessed and used:
It is possible to add an XML Description on a call screen by inserting "GP_XML[n]" (with n being the index of the general_purpose_xml_descriptions, first one is 0) into one of the call screen fkeys settings. See general_purpose_xml_descriptions for a list of available settings.
call_screen_fkeys_on_connected=GP_XML [...] F_HOLD [...]
See this link for details regarding the XML Minibrowser. Example:
[...] <SoftkeyItem> <Name>F2</Name> <Softkey>GP_XML</Softkey> </SoftKeyItem>
An XML Definition can be used by another XML Definition. See more details here.