Project info for Longhall

Created 5 Aug 2001 at 16:12 UTC by Nygard, last modified 5 Aug 2001 at 16:12 UTC by Nygard.

Notes:

This project will be a different kind of environment. Ultimately, it will be a platform that lets objects exist holographically, "in the network", impervious to host failures, censorship, deliberate destruction, or accidental loss.

That ambitious end has humble beginnings. As of today, Longhall includes:

• Publish-subscribe messaging
• XML based object instantiation and parameterization

Publish-Subscribe Messaging
Currently using UDP multicast for unreliable point to multipoint messaging. All messages are objects.

I have no desire to pursue JMS support, nor guaranteed delivery, QoS, or other stuff you find in typical MQ projects. There are plenty of those. The idea here is that unreliability is inherent in distributed computing. It cannot be eliminated, so instead, it should be embraced.

XML based object whooza-whatsits
Suppose object of type "A" has a property "strategy" of type "B". Before an instance of "A" can be used, some entity must select the right class for the strategy, instantiate it, configure its properties, and set it as a property on A.

Traditionally, all of that is done directly in code. This object instantion and configuration allows you to declare all of your object configurations externally. The Realizer can then instantiate and configure your application's objects. This allows a couple of benefits that might not be immediately obvious:

• Multiple products can be built from the same components. (For example, a client-side workspace that mirrors a view into a remote repository.)
• Substituting components requires no code changes.
• The internal linkages of an application are visible. This aids learning, debugging, and extension.
• Tuning parameters become obvious. There are no hidden properties, everything is visible.

License: GPL

This project has the following developers:

• Nygard is a Lead Developer.

New HTML Parser: The long-awaited libxml2 based HTML parser code is live. It needs further work but already handles most markup better than the original parser.

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If you're a C programmer with some spare time, take a look at the mod_virgule project page and help us with one of the tasks on the ToDo list!