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Appia is an open source layered communication toolkit implemented in Java, and licensed under the Apache License, version 2.0. It was born in the University of Lisbon, Portugal, by the DIALNP research group that is hosted in the LaSIGE research unit. This framework provides extended configuration and programming possibilities.
Appia is composed by a core that is used to compose protocols, and a set of protocols that provide group communication, ordering guaranties, atomic broadcast, among other properties.
The Appia core offers a clean way for the application to express inter-channel constraints. This feature is obtained as an extension to the functionality provided by current systems. Thus, Appia retains a flexible and modular design that allows communication stacks to be composed and reconfigured in run-time.