Corpus based preposition selection - HOWTO
The general algorithm for performing corpus based preposition selection is as follows:
- Download a parallel corpus
- Extract patterns which contain prepositions from the source-language corpus
- Align the patterns to their translations in the target-language corpus
- Extract the features and label (the correct preposition from the target-language corpus) for classification.
- Train a model
- Use the trained model in the pipeline
The general toolkit for performing these tasks can be found here.
The training phase is done in two steps:
- Extract patterns in the form of (n|vblex) (pr) (adj | det)* (n|vblex) from the source language corpus and translate the using apertium to the target language.
- Go through the source language file again, matching those same patterns and trying to find their translations in the target language. If a translation is found, extract the features and correct preposition as a training-set example. You could theoretically choose any combination of features, however, the tools provided so far support only 3 different combinations:
- 1-feature model -- extract an example in the following format: sl_nv1-sl_pr-sl_nv2<delimiter>tl_pr
- 2-feature model -- extract an example in the following format: sl_nv1-sl_pr<delimiter>-sl_nv2<delimiter>tl_pr
- 3-feature model -- extract an example in the following format: sl_nv1<delimiter>sl_pr<delimiter>sl_nv2<delimiter>tl_pr
sl_nv1, sl_nv1 and sl_pr stand for the first and second source language noun or verb, and for the source language preposition. tl_prep stands for the target language preposition, and that is the actual label used in classification