PML: A Language Interface to Distributed Voice-Response Units
Wide-area networks such as the Internet support distributed applications that occasionally incorporate services owned and operated by third parties. These third-party network services must be reliable and secure; they must support efficient and responsive applications; finally, they must be cost-effective. Can programming languages contribute to achieving these goals? This paper responds to that question by relating experience with the Phone Markup Language (PML), and its role in a project code-named “PhoneWeb”. The PhoneWeb provides Voice Response Unit (VRU) capabilities to untrusted remote clients by accepting PML programs and executing them: PML acts as the PhoneWeb “service interface”. By using a language as the service interface, we have obtained the performance benefits due to mobile code; and through restrictions on our language we have achieved security and reliability. The resulting service allows us to timeshare the underlying hardware, yielding a solution that is more cost-effective than its alternatives.
KeywordsSystem Call Interactive Voice Response Service Logic Service Interface Concrete Syntax
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