User:Randykahle/draft - NetKernel
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NetKernel is an implementation of a resource-oriented computing abstraction. It embodies ideas from the World Wide Web and the Unix operating system. It can be thought of as an internet-like operating system running on a microkernel within a single computer.
NetKernel was developed by 1060 Research and is offered under a dual open source and commercial software license.
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[edit] Concepts
A resource is identifiable information within a computer system. Resources are an abstract notion and they cannot be manipulated directly. When a resource is requested, a concrete, immutable representation is provided. This is directly analogous to the way the World Wide Web functions. On the Web, a URL address identifies a globally accessible resource. When a browser issues a request for the resource it is sent a representation in the response.
A resource is identified by an address within an address space. In NetKernel Uniform Resource Identifier (URI) addresses are used to identify all resources. Unlike the Web, which has a single global address space, NetKernel supports an unlimited number of address spaces and mapping relationships between the address spaces.
The fundamental operation in NetKernel is a resource request, or request. A request consists of the resource URI address and a verb. The supported verbs are SOURCE, SINK, NEW, DELETE, and EXISTS. Each request is dispatched to the microkernel which assigns it to a thread and schedules it for processing.
NetKernel supports a variety of URI schemes and introduces new ones specifically applicable to URI addressing within a software system.
[edit] Programming
The fundamental instruction in NetKernel is a resource request, specified by a URI. Mechanisms that sequence URI requests are located above the microkernel. In the current Java-based implementation, requests are dispatched using a Java API. This implies that any language that can call a Java API can be used to program NetKernel.
The set of languages currently (January 2007) supported includes: Java, Ruby, JavaScript, Python, Groovy, Beanshell, DPML, and XML related languages such as XQuery, etc. The URI specification itself has sufficient richness to express a functional programming language.
[edit] Active URI Scheme
The active URI scheme was proposed by Hewlett-Packard as a means to encode a functional program within a URI.
active: {function-name} [+ {parameter-name} @ {parameter-value-URI}]*
For example, the following URI calls a random number generator
active:random
and the following uses an XSLT service to transform an XML document with an XSLT stylesheet:
active:xslt+operator@file:/style.xsl+operand@file:/document.xml
Because the argument values may be URI addresses themselves, a tree-structured set of function calls can be encoded in a single URI.
[edit] Transports
Transports are a mechanism used to introduce requests from outside of NetKernel to the NetKernel address space. Transports are available for the HTTP protocol, JMS (Java Messaging Service), and CRON. Other transports can be easily added as they are independent from the rest of NetKernel.
The role of the transport is to translate an external request based on one protocol into a NetKernel request with a URI and a specific verb (SOURCE, SINK, etc.) and then to send the returned representation back to the client via the supported protocol.
Two mappings are handled by a transport. The first is between the address space of the externally supported protocol to the internal NetKernel address space. And the second is between the verb or action specified externally into a NetKernel verb.
For example, in the case of the HTTP transport, the external address space is a sub-space of a URL. The following mapping illustrates this point.
http://www.mywebsite.com/publications/...
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v
file:/src/publications/...
In addition, the HTTP protocol supports methods such as GET, PUT, HEAD, etc. which are mapped to NetKernel verbs.
[edit] Scripting Languages
A mechanism is needed to issue the URI requests, capture the returned representations, and communicate with clients.
NetKernel uses
Scripting languages are executed by their runtime engine, which it itself a service. For example, the Beanshell language runtime will run a program contained in the file file:/program.bsh with the following:
active:beanshell+operator@file:/program.bsh
[edit] Architectural Consequences
[edit] History
[edit] External links
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