LYCOS RETRIEVER 
Microkernel
built 185 days ago
The Microkernel architectural pattern applies to software systems that must be able to adapt to changing system requirements. It separates a minimal functional core from extended functionality and customer-specific parts. The microkernel ... serves as a socket for plugging in these extensions and coordinating their collaboration.
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Microkernel servers are essentially daemon programs like any others, except that the kernel grants some of them privileges to interact with parts of physical memory that are otherwise off limits to most programs. This allows some servers, particularly device drivers, to interact directly with hardware.
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The KeyTECH Microkernel is based on objects, capabilities, and messages. Objects are an encapsulation of some data and a program that manipulates that data. Objects are generally programs outside the Microkernel, much like the servers of some systems or the tasks of other systems. Capabilities are special tokens that designate Objects and allow the holder to send a message to the designated Object. Messages are composed of a string of bytes and 4 capabilities.
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Microkernel development came to be seen as a way to apply this Unix design model, common in userland functions, to the kernel itself. During the mid 80s, academia plunged into microkernel development. One of the more famous projects that involved microkernel design principles was CMU's Mach project.
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What distinguishes the KeyTECH Microkernel from other Microkernels is the total reliance on capabilities without any other mechanisms. There are no other mechanisms that add complexity to the ideas or to the implementation. In a KeyTECH system, a "task" is created, described, and manipulated by capabilities. KeyTECH itself knows very little about such tasks. From the KeyTECH view there are only Nodes and Pages. Some of the Nodes are on the CPU queue or various waiting queues and ... have a process associated with them.
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Microkernel-based architectures should particularly support extensibility and customizability, robustness including reliability and fault tolerance, protection and security. After disastrous results in the early 90's, the microkernel approach now seems to be promising, although it still bears a lot of research risks.
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