Service provider efforts to expose network functionality via open application programming interfaces (APIs) have proved mixed at best, but vendors and operators are hoping that making those interfaces more Web-friendly may help the cause.

BroadSoft this week launched a set of so-called RESTful versions of its APIs, which help carriers and developers build Web applications with its carrier-grade VoIP platform. The new Xtended Services Interface, or XSI, is part of BroadSoft’s larger Xtended Program for enabling the creation of telecom mashups. Other API programs, specifically British Telecom’s Web21C SDK, are also seemingly headed the RESTful route.

REST, or representational state transfer, is a style of software architecture that many claim is responsible for the Web’s rapid growth. It is a more loosely coupled style of development, based on Web standards such as HTTP, XML and the location concept of the URL/URI. It is an alternative to building Web services using SOAP, or Simple Object Access Protocol, which also works over HTTP but relies on remote procedure call (RPC) methods more similar to past programming approaches such as DCOM or CORBA.

Put all of those developer acronyms aside, and what’s left is the desire for service providers to continue to move its application- and service-building approaches ever closer to the Web world. REST-based interfaces should appeal to a class of Web-centric developers that not only don’t know network protocols but are a step removed from enterprise-style Java/SOAP-driven development as well.

“By making the XSI available, we’re speaking the language of most software developers,” said Scott Hoffpauir, BroadSoft’s chief technology officer.

In addition to its new RESTful interfaces, the BroadSoft Xtended Developers Program includes Open Client Interface-Provisioning (OCI-P), Client Application Protocol (CAP), VoiceXML and ccXML interfaces.

RESTful APIs are critical if a more open, mashup style of development is to truly take hold in telecom. BT, whose Web21C SDK was one of the first to expose telco APIs, is working on RESTful versions of its APIs, said Tim Stevens, BT’s SDK evangelist, in a recent interview with Telephony.

“We’re looking at making our APIs more Web-like,” Stevens said. “Our ultimate vision is to let developers voice-enable any application. WS-SOAP public key certificates are more heavyweight, which means that they are things like client-side mashups that aren’t really possible to do with our [API] exposure right now.”

But even as some operators and vendors push more Web-like APIs and the promise of open, long-tail mashups, others see that style of programming as a dead end for telcos.