COREFL: Corpus of English as a Foreign Language


Oct. 2021


What is tagging?

Part-of-Speech tagging (POS tagging) consists of automatically assigning tags to words. Each word is tagged (=labelled) according to its linguistic category. A simplified form of POS tagging is similar to what we used to do at school when identifying words as Nouns, Verbs, Adjectives, Prepositions. For example, the word ‘friend’ will be tagged as NCS, which means that it is a Noun, Common, Singular.

Which COREFL subcorpora are tagged?

In this version of COREFL (version 1), the English and Spanish components of COREFL have been POS tagged: the L2 English learner subcorpora, the L1 Spanish native subcorpus, and the L1 English native subcorpus.

What is POS tagging used for in COREFL?

When searching the COREFL corpus, you can do two types of searches:

When doing an advanced search, the corpus must have been previously POS tagged. This is why COREFL has been POS tagged.

Which tags have been used?

COREFL subcorpora have been automatically POS tagged with the FreeLing tagger. For an interpretation of the tags, see the FreeLing tagset description and, more specifically, the English tagset and the Spanish tagset. You can also see an online demo of FreeLing where you can introduce your own text and it will be automatically tagged.

An important note on automatic POS tagging

Please note that in this version of COREFL the POS tagging has been done automatically, which implies that some words produced by learners might have been incorrectly categorised due to the very nature of learners’ language. This is so because the POS tagger automatically applies English native categories onto the learner language (L2 English), e.g.:

Despite the shortcomings of automatic tagging, we believe that this type of tagging is still very useful for those users who want to do complex searches, e.g., two advanced searches comparing the word order Noun+Adjective (dog white) vs. Adjective+Noun (white dog). The automatic tagger may not always tag learners’ misspelled adjectives as adjectives. However, properly spelled adjectives, which are the majority, will be correctly tagged as adjectives. Therefore, automatic tagging in a learner corpus is more useful than no tagging at all.