Task ideas for Google Code-in/Tokenisation for spaceless orthographies
Objective[edit]
The objective of this task is to investigate how to best tokenise sentences in South and East Asian languages into words. Sentences in these languages are usually not written with spaces to show word boundaries.
The "regular" method is Apertium, both lttoolbox and hfst, is LRLM, which isn't able to deal with spaceless (and tokenisation-ambiguous) sentences.
Example[edit]
Imagineforamomentthatenglishwerewrittenwithoutspaces.
Given a fairly complete dictionary of English words it should be possible to generate all the possible ways of splitting up the sentence into words that are found in the dictionary:
Imagine·for·a·moment·that·english·were·writ·ten·with·out·spaces Imagine·fora·moment·that·english·were·writ·ten·with·out·spaces Imagine·for·a·moment·that·english·were·written·with·out·spaces Imagine·fora·moment·that·english·were·written·with·out·spaces Imagine·for·a·moment·that·english·we·rewritten·with·out·spaces Imagine·fora·moment·that·english·we·rewritten·with·out·spaces Imagine·for·a·moment·that·english·were·writ·ten·without·spaces Imagine·fora·moment·that·english·were·writ·ten·without·spaces Imagine·for·a·moment·that·english·were·written·without·spaces Imagine·fora·moment·that·english·were·written·without·spaces Imagine·for·a·moment·that·english·we·rewritten·without·spaces Imagine·fora·moment·that·english·we·rewritten·without·spaces
Prior work:
Tasks[edit]
Literature review[edit]
Search on Google for papers and programs about word segmentation / tokenisation for the language in question. Make a report about what you find.
Input/output code[edit]
The input should be a sentence, and the output should be a lattice, for example:
^Imagine/Imagine$ ^fora/fora/for+a$ ^moment/moment$ ^that/that$ ^english/english$ \ ^werewritten/were+writ+ten/were+written/we+rewritten$ ^without/with+out/without$ ^spaces/spaces$
Algorithms[edit]
- Longest-match left-to-right (LRLM)
- Maximal matching
- N-gram models
It should be possible to have for each word in the dictionary its possible parts-of-speech. Given this it should be possible to calculate n-gram co-occurrence probabilities, and use these to rank the possible segmentations.
Evaluation[edit]
Take about 3000 words of text in the language (about 6 pages) and split it into sentences. Then manually split the sentences into tokens. Compare the performance of the algorithm(s) you have implemented against the manually tokenised sentences.
