# Extending biblatex to support multiple scripts

As regular readers will know, I’ve taken an interest in biblatex since it was first developed. Since the original author disappeared, I’ve been at least formally involved in maintain the code. So far, that’s been limited to tackling a few tricky low-level TeX issues, but there are some bigger issues to think about.

Philip Kime, lead Biber and biblatex developer, is keen to extend the LaTeX end to supporting multiple scripts. The Biber end is already done (in the ‘burning edge’ version), and writes to the .bbl file in the format:

\field{form=original,lang=default}{labeltitle}{Title}
\list{form=original,lang=default}{location}{1}{%
{Москва}%
}
\list{form=romanised,lang=default}{location}{1}{%
{Moskva}%
}

However, that presents a big issue: how to do that without breaking every existing style. Supporting scripts means we need an additional argument for a very large number of commands: some of them need to have two optional arguments, and some of them need to be expandable:

\iffieldundef[form=original,lang=default]{....}

Reading (two) optional arguments and working through keyval options expandably is tricky, which is where I come in. The natural way for me to solve the first problem is to use LaTeX3, and the xparse package. However, that’s a big change for biblatex, so before I (and the rest of the biblatex team) go for this I though it would be worth raising the issue and looking for opinions. The alternative is to write the code into biblatex directly, but it’s complicated and as I’ve already done the job once I’m reluctant to do this!

So, what I want to know is ‘What do users think?’ Is it reasonable to require xparse as part of biblatex?