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The kernel is designed to be simple and limited in its capabilities: it wires functional units together. Capabilities such as service discovery, reliability, support for transport protocols, etc. are provided through extensions. The kernel extension model is based on the SCA 1.0 Java programming and assembly model. In otherwords, the kernel uses SCA to bootstrap itself. The mechanics of how this is done are described in detail elsewhere Kernel Architecture.
Federation
An Overview of Extensions
The kernel is divided into a number of modules, among them spi and core. The spi module defines extension points