XDuce: A Typed XML Processing Language

Overview

XDuce ("transduce") is a typed programming language that is specifically designed for processing XML data. One can read an XML document as an XDuce value, extract information from it or convert it to another format, and write out the result value as an XML document. Since XDuce is statically typed, XDuce programs never crash at run time and the resulting XML documents always conform specified types.

XDuce has several notable features.

1. XDuce features regular expression types, which are similar in spirit to Document Type Definitions (DTD).
2. XDuce provides a powerful notion of subtyping. (It allows any subtyping relation that you may expect from your intuition on inclusion relation of regular expressions.) It not only gives substantial flexibility in programming, but also is useful for schema evolution or integration.
3. XDuce supports regular expression pattern matching . In addition to ML-like patterns, we can match values against regular expression types.

Implementation Status

This implementation is a part of our ongoing research. The language design has not been finished, and some algorithmic issues in type checking and the run-time system still remain. This language system is likely to be drastically changed in near future. So please do not depend on this software. On the other hand, any comments and suggestions are welcome!

System Requirements

XDuce system is solely written in the O'Caml language. In principle, XDuce should run on any platform that O'Caml supports. In particular, we have checked that XDuce works on the following.

• SunOS 5.7
• Intel Linux
• LinuxPPC
• IRIX

We have not yet tested compilation on Windows. However, since recent versions of O'Caml and the libraries that XDuce depends on support Windoes with Cygwin, XDuce should work on this platform in principle.

Building XDuce

1. Make sure that GNU make or its equivalent is installed.
2. Install O'Caml (newer than 3.04; older ones may not work) if not yet installed.
3. Install the findlib tool (newer than 0.6.2).
4. Install the following libraries in this order.
   1. netstring (newer than 0.10.1)
   2. PXP (newer than 1.1.3)

   Note: You have to build each library by typing "make opt" in order to build xduce by the native O'Caml compiler (type "make all" if you want to compile the bytecode version of xduce).

5. Compile XDuce as follows.
   1. tar xvfz xduce-xxx.tar.gz (where xxx is the version number of XDuce you downloaded).
   2. cd xduce-xxx
   3. make

   It will produce an executable file named xduce.opt in the xduce-xxx directory.

   On platforms where native O'Caml compiler is not supported, still bytecode version may work. For this compilation, type:

   make debug

   This will yield an executable file xduce. The usage is the same.

6. At the moment, we do not provide any automatic installation mechanism. You may move the executable wherever you want. Note, however, it directly refers to the xduce-xxx/lib directory. Make sure that this directory is accessible when you use the executable. Or, if you need to move the lib directory, then specify the new location by -path option:

   xduce.opt -path <new-location> ...

Usage

type

xduce.opt <XDuce program file>

xduce.opt -help

Documentation

There is no user's manual since the language design is not yet settled. The programs found in "examples" directory would be useful for understanding the language. Also, the files in "lib" directory (such as "pervasive.q" and "xml.q") would be worth seeing.

For more information, visit our web page:

http://xduce.sourceforge.net

Contact

Acknowledgement

• We especially thank Volker Renneberg for his tremendous contributions to our implementation in bug reports, suggestions, and additional code.
• Some sources files from the bibtex2html tool by Jean-Christophe Filliatre and Claude Marche are incorporated (in bibtex directory).