, Messaging, Policy Management, Quality of Service. Transport interface: CORBA, WSDL (Web Services). The Parlay/OSA Gateway consists of several SCS: functional entities that pro- vide Parlay/OSA interfaces toward applications. Each SCS is seen by applications as one or more Service Capability Features (SCF): abstractions of the functionality offered by the network, accessible via the Parlay/OSA API. Sometimes they are also called services. The Parlay/OSA SCFs are specified in terms of interface classes and their methods. One of the Parlay/OSA SCSs is called the Parlay/OSA Framework, and is always present, one per network. The functionality of the OSA Framework is grouped in two main sets of interfaces: Interfaces to the third-party applications, which provide mechanisms for controlling their access to the network (authentication and authorization), for ensuring the integrity of the network (e.g., load and fault management), and for the applications to discover the functionality that the operator's network exports via the OSA API. Interfaces to the other SCSs, which provide mechanisms for registration in the framework of their SCFs SO that the applications may discover them; they also provide the necessary access control mechanisms to allow the framework functionality to be provided by an independent business entity (multidomain). To enable the availability and usage of the Parlay APIs, there was the require- ment to publish the capabilities of the network for software developers, and on the other hand the demand for enterprise applications to exploit the capabilities of the Telecom network. Hereby, Web services are a key software development technology which triggered the evolution of Parlay X. Parlay X is a subset of the Parlay APIs, and provides a higher-level Web services abstraction of the more complex Parlay/OSA APIs. While Parlay/OSA provide rich function in an asynchronous programming model, are CORBA-based implemen- tations, and are primarily used for Service provider-hosted applications, the Parlay X Web