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This gem is unmaintained. A fork with active maintainers is available: cacofonix

The ONIX standard is a somewhat verbose XML format that is rapidly becoming the industry standard for electronic data sharing in the book and publishing industries.

This library provides a slim layer over the format and simplifies both reading and writing ONIX files in your ruby applications.

This replaces the obsolete rbook-onix gem that was spectacular in its crapness. Let us never speak of it again.

Feature Support

This library currently only handles ONIX 2.1 files (all revisions). At some point I'll need to work out what to do about supporting ONIX 3.0 files. I suspect a separate library will be the simplest solution.

ONIX::Reader only handles the reference tag versions of ONIX 2.1. Use ONIX::Normaliser to convert any short tag files to reference tags.

ONIX::Writer only generates reference tag ONIX files.

It baffles me why anyone thought designing two parallel versions of the ONIX spec was a good idea. Use reference tags my friends, and let short tags fade away into irrelevant obscurity.

DTD Loading

To correctly handle named entities when reading an ONIX file, this gem attempts to load the DTD describing the ONIX format into memory. By default, this means each file you read will require several hundred Kb of data to be downloaded over the net.

This is obviously not desirable in most cases. To avoid it, you need to add copies of the ONIX DTDs into your system XML catalog. On Debian and Ubuntu systems, the quickest way to do that is to build and install the package available @


gem install onix


See files in the examples directory to get started quickly. For further reading view the comments to the following classes:

  • ONIX::Reader - For reading ONIX files
  • ONIX::Writer - For writing ONIX files
  • ONIX::Normaliser - For normalising ONIX files before reading them. Fixes encoding issues, etc
  • ONIX::Lists - For building hashes of code lists from the ONIX spec


This library is distributed under the terms of the MIT License. See the included file for more detail.


All suggestions and patches welcome, preferably via a git repository I can pull from. To be honest, I'm not really expecting any, this is a niche library.

Further Reading


A convenient mapping between ruby objects and the ONIX XML specification







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