CCXML 1.0-W3C Development Guide

<transition> element

The <transition> element is used to catch incoming asynchronous events. The first <transition> element encountered in the document order that matches up with a specific event will be the first one executed by the CCXML interpreter.

Once a <transition> has been encountered, the tags nested within the element will then be executed in document order. If an event is thrown, and no matching <transition> is exeistent in the document, then the event will be dropped entirely, (and there will consequently be a message in the Voxeo logger indicating that an unhandled event was encountered).

Should any subsequent events arrive while a <transition> is already in progress, this second event will be placed into the event queue for later processing.

usage

attributes

cond	Data Type: (ECMAScript Expression)	Default: True
	The cond attribute specifies an ECMAScript expression which can be evaluated to 'true' or 'false'. A condition must evaluate to 'true' in order for any enclosed operations to be performed.
event	Data Type: (ECMAScript Expression)	Default: none - attribute is required
	The event attribute denotes the matching event type used to kick off the code contained within the <transition> element. Event types can be a user-defined, dot separated ECMAScript string of any length, or, (more commonly), it can indicate a platform-defined event type. Note that the '*' suffix is a wildcard, and will match zero or more characters of any event name.
name	Data Type: (variable name)	Default: none - attribute is optional
	The name attribute denotes that the unique variable that is to receive the event indicated in the <transition> element.
state	Data Type: STRING	Default: none - attribute is required
	Indicates the current possible state(s) of the eventhandler.

parents

children

code samples

<1.0 transition>

<?xml version="1.0" encoding="UTF-8"?>
<ccxml version="1.0" xmlns="http://www.w3.org/2002/09/ccxml">

<meta name="author" content="Jeff Menkel"/>
<meta name="copyright" content="2007 Voxeo Corporation"/>
<meta name="maintainer" content="YOUR_EMAIL@HERE.COM"/>

<eventprocessor>

<transition event="connection.alerting">
<log expr="'*** Incoming call detected ***'"/>
<accept/>
</transition>

<transition event="connection.connected">
<log expr="'*** The call was answered ***'"/>
<disconnect/>
</transition>

<transition event="connection.disconnected">
<log expr="'*** Disconnecting ***'"/>
<exit/>
</transition>

</eventprocessor>
</ccxml>

additional links

W3C Specification

ANNOTATIONS: EXISTING POSTS

mtatum111

10/9/2008 3:36 PM (EDT)

can you explain the difference between the event attribute and the name attribute for <transition>

It appears that both of them are very similar.

Thanks

voxeoAlexBring

10/9/2008 4:49 PM (EDT)

Hey Melissa,
The name attribute is actually now an outdated part of the transition element. It has been replaced by a much better feature that is built into ccxml 1.0-W3C. The newer feature is "event$". For example using it would look like this:
instead of:
[color=red]
<transition event="connection.connected" name="evnt">
<assign name="conn_id" expr="evnt.connectionid"/>
</transition>
[/color]
it would look like this:
[color=red]
<transition event="connection.connected">
<assign name="conn_id" expr="event$.connectionid"/>
</transition>
[/color]
Hope this helps to clear up any confusion, if you have any other questions please don't hesitate to ask.

Standing by,
Alex

mho

9/16/2009 3:52 PM (EDT)

Is there a way to specify multiple states in a <transition> tag.
I am only asking because the text of the description says "Indicates the current possible state(s) of the eventhandler." and this would certainly make the script look better.

I suppose we can catch the event and use a construct like:
<if cond="statevariable=='specialcase'">... </if>
that is OK but not sexy.

Thanks
Mho

jdyer

9/16/2009 6:07 PM (EDT)

Hello Mho,

Yes this can most certainly possible, you actually want to use a space delimited list. I have put together a small example to help illustrate this which you will find below:

<?xml version="1.0" encoding="UTF-8"?>
<ccxml version="1.0">
<var name="myVar" expr="'init1'"/>
<var name="counter" expr="0"/>
<eventprocessor statevariable="myVar">
<transition event="ccxml.loaded">
<log expr="'******* CCXML LOADED'"/>
<send data="'goto.BlockOne'" target="session.id" delay="'1s'"/>
<send data="'user.DIE_ZOMBIE_DIE'" target="session.id" delay="'10s'"/>
</transition>
<transition event="goto.BlockOne">
<send data="'goto.BlockTwo'" target="session.id" delay="'1s'"/>
<assign name="myVar" expr="'init1'"/>
</transition>
<transition event="goto.BlockTwo">
<send data="'goto.BlockOne'" target="session.id" delay="'1s'"/>
<assign name="myVar" expr="'init2'"/>
</transition>
<transition event="SEND.SUCCESSFUL" state="init1 init2">
<log expr="'******* This happens in more then one state **'"/>
<assign name="counter" expr="counter+1"/>
<log expr="'******* Happened ' + counter + ' Times'"/>
<send data="'user.test'" target="session.id" delay="'1s'"/>
</transition>
<transition event="user.DIE_ZOMBIE_DIE">
<exit/>
</transition>
</eventprocessor>
</ccxml>

I do hope this helps, and if there are any other questions please let us know as we are most certainly standing by to assist!

Regards,

John Dyer
Customer Engineer
Voxeo Support

mysteriocharan

12/25/2011 10:50 AM (EST)

Hi,

I'm new to CCXML. Sorry if the question is silly. Can someone please tell me how the "State" property of the "Transition" event work?

Thanks,
Charan

voxeoJeffK

12/27/2011 11:58 AM (EST)

Hello Charan,

This tutorial covers it in some detail:

http://docs.voxeo.com/ccxml/1.0-final/t_3ccxml10.htm

but basically CCXML is at its core a state machine. In practice setting the state allows for different event handling for the same event type based on the present state.

Regards,
Jeff Kustermann
Voxeo Corporation