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`xmlfs` is a translator that provides access to XML documents through the
filesystem.

# How to Use xmlfs

	xmlfs - a translator for accessing XML documents

This is  only an alpha version.   It works in read  only.  It supports
text  nodes and  attributes. It  doesn't do  anything fancy  like size
computing, though. Here is an example of how to use it:

    $ wget http://cvs.savannah.nongnu.org/viewvc/*checkout*/hurdextras/xmlfs/example.xml?content-type=text%2Fplain;
    $ settrans -ca xml /hurd/xmlfs example.xml  #the website says to use ./xmlfs
    $ cd xml; ls
      library0 library1
    $ cd library0; ls -A
      .text1  .text2  @name  book0  book1  book2  sub-library0  sub-library1
    $ cat .text2

CDATA, again !

    $ cat book0
      <book>
      <author>Mark Twain</author>
      <title>La case de l'oncle Tom</title>
      <isbn>4242</isbn>
      </book>
    $ cat book0/author/.text
      Mark Twain

As  you can  see,  text nodes  are  named .textN,  with  N an  integer
starting from 0. Sorting is supposed to be stable, so you get the same
N every time you access the same  file. If there is only one text node
at this level, N is ommitted. Attributes are prefixed with @.

An  example file,  example.xml, is  provided. Of  course, it  does not
contain anything  useful. xmlfs  has been tested  on several-megabytes
XML documents, though.

Comments are welcome.

	-- Manuel Menal <mmenal@hurdfr.org>

# TODO
- Handle memory usage in a clever way:
     - do not dump the nodes at each read, try to guess if read()
       is called in a sequence of read() operations (e.g. cat reads
       8192 bytes by 8192 bytes) and if it is, cache the node
       contents. That'd need a very small ftpfs-like GC.
     - perhaps we shouldn't store the node informations from
       first access to end and have a pool of them. That might come
       with next entries though.
- Handle changes of the backing store (XML document) while running.
    (Idea: we should probably attach to the XML node and handle
     read()/write() operations ourselves, with libxml primitives.)
- Write support. Making things like echo >, sed and so on work is
   quite obvious. Editing is not -that- simple, 'cause we could
   want to save a not XML well-formed, and libxml will just return
   an error. Perhaps we should use something like 'sync'.
- Handle error cases in a more clever way ; there are many error
   conditions that will just cause xmlfs to crash or do strange
   things. We should review them.
- Make sorting *really* stable.

# TODO WISHLIST
--------

- Kilobug suggested a --xslt option that would make xmlfs provide
   a tree matching the XSLT-modified document.
   (Problem: In this case we cannot attach easily to the .xml 'cause
    the user would loose access to theirs original document. Perhaps
    we should allow an optional "file.xml" argument and check if it
    is not the same as the file we are attaching to when --xslt is
    specified.)
- DTD support ; perhaps XML schema/RelaxNG when I'm sure I understand
   them ;-)


# Source

<http://www.nongnu.org/hurdextras/#xmlfs>