NL Reference Corpus

Revision as of 18:01, 17 April 2014

The NL Reference Corpus (NC) is the corpus used to prepare and to assess grammars for sentence-based UNLization. It is divided in 6 different levels according to the Framework of Reference for UNL (FoR-UNL):

• NC-A1: NL Reference Corpus A1
• NC-A2: NL Reference Corpus A2
• NC-B1: NL Reference Corpus B1
• NC-B2: NL Reference Corpus B2
• NC-C1: NL Reference Corpus C1
• NC-C2: NL Reference Corpus C2

Methodology

As a natural language corpus, the NC varies for each language. It is derived from a base corpus to be compiled and processed according to the following criteria:

1. The Base Corpus must have at least 5,000,000 tokens (strings isolated by blank space and other word boundary markers). It must be representative of the contemporary standard use of the written language, and should include documents from as many different genres and domains as possible.
2. The Base Corpus must be segmented (in sentences) and tagged for POS.
3. The segmented corpus is used to calculate the average sentence length (ASL), which is the median of the length (in words) of all sentences.
4. The tagged corpus is used to extract the linear sentence structures (LSS), which are sequences of POS, and to calculate their frequency of occurrence.
5. The average sentence length (ASL) and the linear sentence structures (LSS) are used to generate the NC templates, as follows:
   • NC-A1 = 1,000 most frequent LSS where length <= 15th percentile (very small sentences)
   • NC-A2 = NC-A1 + 1,000 most frequent LSS where 15th percentile < length <= 30th percentile (small sentences)
   • NC-B1 = NC-A2 + 1,000 most frequent LSS where 30th percentile < length <= 45th percentile (small medium-size sentences)
   • NC-B2 = NC-B1 + 1,000 most frequent LSS where 45th percentile < length <= 60th percentile (long medium-size sentences)
   • NC-C1 = NC-C1 + 1,000 most frequent LSS where 60th percentile < length <= 80th percentile (long sentences)
   • NC-C2 = NC-C2 + 1,000 most frequent LSS where length > 80th percentile (very long sentences)
6. The NC templates are used to compile the NC corpora: the training corpora and the testing corpora. The training corpora consists of 1 exemplar of each LSS, and will be used to prepare the grammar. The testing corpora consists of 4 exemplars of each LSS randomly selected in the Base Corpus. The whole NC corpora (i.e., 5 exemplars for each LSS) is used to calculate the F-measure, which is the parameter for assessing the precision and the recall of the grammars.

Files

• Arabic
  • Source: Wikipedia
  • Total number of distinct sentences: 801,258
  • Corpus
    • Corpus NC_ara_A1 (length <= 9: 141,988 sentences)
    • Corpus NC_ara_A2 (9 < length <= 13: 150,406 sentences)
    • Corpus NC_ara_B1 (13 < length <= 17: 146,178 sentences)
    • Corpus NC_ara_B2 (17 < length <= 22: 141,376 sentences)
    • Corpus NC_ara_C1 (22 < length <= 32: 165,455 sentences)
    • Corpus NC_ara_C2 (length > 32: 165,616 sentences)