Open standardised APIs can be used to provide the glue between (IT) applications and telecom network functionality via secure, measured, and billable interfaces, making the applications implementing the services independent from the underlying network technology.

By releasing developers from underlying networks and environments, such open APIs to access network services expands the possible set of applications and allows network function owner to change implementations without changing applications .

The 3GPP, in collaboration with its specification partners ETSI TISPAN and Parlay Group industry consortium, has produced the OSA APIs (3GPP TS 23.198, 3GPP TS 29.198), a set of technology-independent functionally-rich interfaces for a broad range of telecommunications enablers including Call Control, Messaging, Location, Presence, Policy, Charging etc., and a set of abstracted Telecom Web Services, Parlay X (3GPP TS 23.198, 3GPP TS 29.199).

The Parlay APIs and Web Services may be used to promote easier access to and exploitation of both Parlay Service Capabilities and OMA enablers in the global developer community.

The Parlay In OSE (PIOSE) Enabler provides an OMA perspective on the use of Parlay and Parlay X as part of the OSE [PIOSE]. This enabler provides further background and analysis on Parlay architecture and principles.