</grammar>
</field><filled>
<result name=”yes”>
<goto next=”#proxy_voicemail”/>
</result>
<result name=”no”>
<goto next=”#disconnect”/>
</result>
</filled>
</form>
</vxml>In this example, the system will play the audio prompt, “Do you want to
leave a message? Say yes or no.” The grammar is defined to be “yes” or “no,”
and this is used by the speech-recognition system to make a decision. The SIP
service logic will then perform the routing to the voicemail server or discon-
nect the call, depending on the outcome of the VoiceXML script.Summary
SIP provides an extremely flexible set of tools for service creation and imple-
mentation. The architectures and tools described in this chapter should allow
the development of many different services in a SIP-enabled network. The
large portfolio of available development tools and the open nature of these
tools will enable the development of many domain-specific communication
services by third-party developers. For example a courier or transportation
company may develop a Presence-based communication application that
allows tracking and contacting any of the fleet workforce according to certain
criteria that are business-specific for the company. Future developments of SIP
are discussed in Chapter 21.References
[1] “Framework for SIP Call Control Extensions” by B. Campbell. IETF Inter-
net draft, work in progress, March 2001.
[2] “CPL: A Language for User Control of Internet Telephony Services” by
Lennox and H. Schulzrinne. IETF RFC 2824, 2001.
[3] “Extensible Markup Language (XML) 1.0 (2nd edition)” by T. Bray, J. Paoli,
and C.M. Sperberg-McQueen.W3C Recommendation REC-xml-20001006,
World Wide Web Consortium (W3C), October 2000.150 Chapter 7