Rethinking tokenisation in the pipeline

At the moment tokenisation is done longest-match left-to-right using the morphological analyser and an alphabet defined for breaking up unknown words.

This has some advantages ...

• It means that multiwords can be included in the dictionary and tokenised as a single unit
• It combines two parts of the pipeline that have complementary information, tokenisation and morphological analysis.

However it has some disadvantages:

• Not having a standard fixed tokenisation scheme makes using other resources harder, and makes it harder for other people to use our resources.
• Ambiguous paths need to be encoded in the lexicon (using +)

Historically,

• We did not have apertium-separable or any other way of merging analyses outside of transfer.
• Unicode support was not as widely used

Current issues

• Splitting tokens that are alphabetic but not in the <alphabet>, e.g. ^Bala$š^evi$ć.

Thoughts

There should be various stages to tokenisation,

• separating whitespace from non-whitespace, no more should we have e.g. ^Bala$š^evi$ć
• morphologically analysing tokens, including those which only appear as part of a multiword
  • contractions (1 token, >1 word)
  • compounds (1 token, >1 word)
• retokenisation for multiwords
  • (>1 token, 1 word)

We should also be able to deal with languages that don't write spaces.