[Corpora-List] Seeking for a free comparable corpus

Mon Jun 16 21:16:43 UTC 2014

Hi Darren, Dekai, and all,

Let me only add that there are a number of definitions around of what constitutes a comparable corpus, and I think none of them is really authorative.

E.g. another one can be found in section 2.1 of the introductory chapter of the book “Building and Using Comparable Corpora”. This chapter can be freely downloaded from http://www.springer.com/computer/ai/book/978-3-642-20127-1 by clicking on “Download sample pages”.

Kind regards,

Reinhard

From: Dekai Wu 
Sent: Monday, June 16, 2014 8:01 PM
To: corpora 
Subject: Re: [Corpora-List] Seeking for a free comparable corpus

Hi Darren,

In a note at http://www.cs.ust.hk/~dekai/library/WU_Dekai/nonparallel.html you can find a systematized overview of relevant discussions on these terminology issues, synthesized from some surveys within some papers by Pascale Fung (who is of course one of the folks who pioneered research in all typies of non-parallel corpora). At least four different levels of (non)parallelism are identified:

parallel corpus
noisy parallel corpus
comparable corpus
quasi-comparable (very-non-parallel) corpus

The note includes an HTML table summarizing the differences (probably can't safely insert the HTML table here, as corpora-list tends to turn HTML formatted stuff into plain text).

References

Pascale Fung & Percy Cheung (2004). Mining very-non-parallel corpora: Parallel sentence and lexicon extraction via bootstrapping and EM. In Dekang Lin and Dekai Wu (editors), Proceedings of the 2004 Conference on Empirical Methods in Natural Language Processing (EMNLP 2004). Barcelona, Spain: July 2004.

Pascale Fung & Percy Cheung (2004). Multi-level bootstrapping for extracting parallel sentences from a quasi-comparable Corpus. In Proceedings of the 20th International Conference on Computational Linguistics (COLING 2004). Geneva, Switzerland: August 2004.

Dekai Wu & Pascale Fung (2005). Inversion Transduction Grammar constraints for mining parallel sentences from quasi-comparable corpora. In Proceedings of the Second International Joint Conference on Natural Language Processing (IJCNLP 2005), Lecture Notes in Computer Science 3651: 257-268.

Hope this helps!
-Dekai
-- 
Dekai Wu
Hong Kong University of Science & Technology (HKUST)
Human Language Technology Center
Department of Computer Science and Engineering

John D Burger wrote: 
No, articles from Wikipedia in different languages are NOT a comparable corpus, for many reasons.

First, most of the time they are a (more or less free) translation of a master/initial one.

Even if this is true (and for most articles it's not, in my experience), the articles quickly deviate as the two language communities begin to make changes. There is of course no particular effort made to keep two articles in sync.

  Second, they are about the same (narrow) subject, while a comparable corpus would be about the same theme but different many  subjects. Examples of comparable corpora would be: original articles in two languages about violations of human rights; or about fashion, or about complaints about health system facilities.

In my opinion, this is a rather narrow definition of comparable corpora, and leaves out many resources that are clearly not parallel, but are nonetheless extremely useful (as evidenced by the substantial amount of research based on such corpora).

As an aside, using the category structure in two Wikipedias, it would be very easy to construct a comparable corpora in almost any domain one wished, if in fact the notion of domain-centeredness is important.

- John Burger
  MITRE

On 14Jun2014, at 10:31, Diana Santos mailto:dianamsmpsantos at gmail.com wrote:

  Hi Darren
No, articles from Wikipedia in different languages are NOT a comparable corpus, for many reasons.

First, most of the time they are a (more or less free) translation of a master/initial one.
Second, they are about the same (narrow) subject, while a comparable corpus would be about the same theme but different many  subjects. Examples of comparable corpora would be: original articles in two languages about violations of human rights; or about fashion, or about complaints about health system facilities.

If you are interested in CLIR you could try the CLEF collections which were precisely created for this.

Second, a parallel corpus is not defined in terms of SENTENCE alignment, unit is a parameter for parallel. So a Wikipedia collection as the one you suggest is a parallel corpus where the unit is the wikipedia article, not the sentence.

Paralell means in a nutshell that you can put the units in direct corespondence (most of them), while comparable means that the selection criteria are the same, but you cannot pair the elements of the two coprora.

I hope to have helped.
Best
Diana

2014-06-14 16:15 GMT+02:00 Darren Cook mailto:darren at dcook.org:
    I'm working on Cross Language Information Retrieval based on
comparable corpora. In order to test my approach, I need a free
comparable corpus between English language and an European language.
      I was just trying to understand the difference between "parallel corpus"
and "comparable corpus". Am I correct in thinking that if an article is
translated (by a professional human translator, or a machine) from one
language to another, such that there is a sentence-level correspondence,
then it is a parallel corpus. Whereas a comparable corpus is one where
the two articles were written about the same subject, but neither is a
translation of the other, and mostly the same knowledge is covered, but
a sentence-level mapping would not exist?

If so, Wikipedia sounds like an ideal source.
E.g.
  http://en.wikipedia.org/wiki/Paris
  http://fr.wikipedia.org/wiki/Paris

  http://en.wikipedia.org/wiki/Association_football
  http://fr.wikipedia.org/wiki/Football

etc.

Darren

--
Darren Cook, Software Researcher/Developer
My new book: Data Push Apps with HTML5 SSE
Published by O'Reilly: (ask me for a discount code!)
  http://shop.oreilly.com/product/0636920030928.do
Also on Amazon and at all good booksellers!

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