File SystemFile System
The module file system
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Module File System

A NetKernel module physically consists of files stored in a tree-structured file system. The module may either be in expanded form, in which case the files are located in the operating system's file system or the module may be contained in a JAR file in which case the module's files are combined into one operating system file that contains a virtual file system. In either case, NetKernel maps the module file system to the physical implementation.

The physical files in the module file system are not available to the internal private address space by default. As discussed in this section on a module's logical structure, a mapping entry using the this element establishes a link between the ffcpl scheme and the module's file system.

For example, if a module has the following physical structure:

resource/
resource/program.idoc
resource/icon.png
test/
test/test-program.js
test/test-program.idoc

The following mapping entry

<mapping>
  <this>
    <match>ffcpl:/resource/.*</match>
  </this>
</mapping>

will make all of the files under the resource directory available within the ffcpl: namespace but will not expose anything under the test directory.

Scratch

The ffcpl provides a mechanism in which a SINK operation to a physical file will not delete the original file - instead it stores the update in a scratch directory. Subsequence SOURCE operations will return the overwritten information from scratch instead of from the module. A DELETE operation on a physical resource will remove the entry in the scratch directory, but will not remove the original file.

This capability is particularly useful for storing temporary state in a module and for overriding configuration information.

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