Dialog chaining and nesting
Dialogs can start other dialogs. Dialogs that start other dialogs are referred to as calling dialogs and the dialogs that are being started are referred to as called dialogs. Two different options are available to complete this action such as dialog chaining and dialog nesting.
With dialog chaining option, one dialog can start another dialog in a way that the calling dialog ends after the called one starts. Therefore, after the called one starts, there is no way to go back to the calling one anymore. For example, in a travel site, you can configure the Flight booking or the calling dialog to end after the Car booking or the called dialog starts. After the Car booking dialog starts the user cannot go back to the Flight booking dialog.
With the dialog nesting option, one dialog can start another dialog but the calling dialog does not end after the called dialog starts. Therefore, you can go back and forth between these nested dialogs. For example, in a travel site, you can configure the Flight booking or the calling dialog to pause after the Car booking or the called dialog starts. After the Car booking dialog starts the user cannot go back and forth between the Flight booking and car booking dialogs.
In both options, the calling dialog references the dialog to be called as target. The called dialog starts with the event the calling dialog emits.
A called dialog can start only by triggering one of its start transitions and can end only by triggering one of its end transitions. In the following code sample, dialog2 must have a start transition, which is triggered by the emission of an event eX. The dialog3 must have a start transition, which is triggered by the emission of an event eY.
...
<transition type="chained">
<source>
<transition-endpoint nameref="portlet1">
<event qname="e1a"/>
</transition-endpoint>
</source>
<target>
<transition-endpoint nameref="dialog2">
<event qname="eX"/>
</transition-endpoint>
</target>
</transition>
...
<transition type="nested">
<source>
<transition-endpoint nameref="portlet1">
<event qname="e1b"/>
</transition-endpoint>
</source>
<target>
<transition-endpoint nameref="dialog3">
<event qname="eY"/>
</transition-endpoint>
</target>
</transition>