[Details] Is an ECMAScript expression which returns a call leg object to associate the new dialog with. The default value of the "callid" attribute is "_event.source", meaning that the dialog instance will be launched for whatever call object generated the previous event (typically a connection.CONNECTION_CONNECTED event). [Attribute Name] 
callid
c a l l i d
c o n i d
s r c
t y p e
n a m e l i s t
d i a l o g i d
d u p l e x