Netlet descriptors

A netlet descriptor is an XML file which tells a node enough for it to load and bind a netlet. Among other things it must tell the node where to get the code from, so it will contain either URLs for the netlet code, or the code itself, or a combination. See Figure .

Figure: A descriptor contains enough information to load and run a netlet. That includes the codebase (or references to it) and an initialisation object among other things.

 

This code, or its URL, allows the node to load the netlet. To bind it, the netlet's initialisation method will be called, but this may require some parameters. So a descriptor also contains a parameter object which it passes to the initialisation method.

Thus a descriptor contains code (and/or URLs for the code) plus an initialisation parameter, and this is enough to load and bind a netlet.

A descriptor is also a key part of a hosting service, when a netlet wants to start up on a new node. By being provided with the netlet's descriptor the new node can create a copy of the netlet and initialise it. On initialisation the netlet can do whatever it needs to run.