mining the web to create minority language corpora
DESCRIPTION
Mining the Web to Create Minority Language Corpora. Rayid Ghani Accenture Technology Labs - Research Rosie Jones Carnegie Mellon University Dunja Mladenic J. Stefan Institute, Slovenia. Who Needs a Language Specific Corpus?. Language Technology Applications Language Modeling - PowerPoint PPT PresentationTRANSCRIPT
Mining the Web to Create Minority Language Corpora
Rayid GhaniAccenture Technology Labs - Research
Rosie JonesCarnegie Mellon University
Dunja MladenicJ. Stefan Institute, Slovenia
Who Needs a Language Specific Corpus?
Language Technology Applications Language Modeling Speech Recognition Machine Translation Linguistic and Socio-Linguistic Studies Multilingual Retrieval
What Corpora are Available?
Explicit, marked up corpora: Linguistic Data Consortium -- 20 languages [Liebermann and Cieri 1998]
Search Engines -- implicit language-specific corpora, European languages, Chinese and Japanese Excite - 12 languages Google - 25 languages AltaVista - 25 languages Lycos - 25 languages
BUT what about Slovenian? Or Tagalog? Or Tatar?
You’re just out of luck!
The Human Solution
Start from Yahoo->Slovenia… Crawl www.*.si Search on the web, look at documents,
modify query, analyze documents, modify query,…
Repetitive, time-consuming, requires reasonable familiarity with the language
Task
Given: 1 Document in Target Language 1 Other Document (negative example) Access to a Web Search Engine
Create a Corpus of the Target Language quickly with no human effort
Algorithm
Query Generator WWWSeed Docs
Language Filter
Web
Word Statistics
Initial Docs
Build Query
Filter
Relevant
Non-Relevant
Learning
Query Generation
Examine current relevant and non-relevant documents to generate a query likely to find documents that ARE similar to the relevant ones and NOT similar to non-relevant ones
A Query consists of m inclusion terms and n exclusion terms e.g +intelligence +web –military
Query Term Selection Methods
Uniform (UN) – select k words randomly from the current vocabulary
Term-Frequency (TF) – select top k words ranked according to their frequency
Probabilistic TF (PTF) – k words with probability proportional to their frequency
Query Term Selection Methods
RTFIDF – top k words according to their rtfidf scores
Odds-Ratio (OR) – top k words according to their odds-ratio scores
Probabilistic OR (POR) – select k words with probability proportional to their Odds-Ratio scores
Evaluation
Goal: Collect as many relevant documents as possible while minimizing the cost
Cost Number of total documents retrieved from the Web Number of distinct Queries issued to the Search Engine
Evaluation Measures Percentage of retrieved documents that are relevant Number of relevant documents retrieved per unique query
Experimental Setup
Language: Slovenian Initial documents: 1 web page in Slovenian, 1
in English Search engine: Altavista
Results
Results – Precision at 3000
0
10
20
30
40
50
60
70
80
90
100
Length=1 Length=3 Length=5 Length=10
OR
POR
TF
PTF
UN
Percentage of Target Docs after 3000 Docs Retrieved
Results – Docs Per Query
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Length=1 Length=3 Length=5 Length=10
OR
POR
TF
PTF
UN
Results - Summary
In terms of documents: For lengths 1-3, Odds-Ratio works best
In terms of queries: Odds-Ratio is consistently better than others
Long queries are usually very precise but do not result in a lot of documents (low recall)
Further Experiments
Comparison to Altavista’s “More Like This” Better performance than Altavista’s feature
Keywords Similar results when initializing with keywords
instead of documents
Other Languages Similar results with Croatian, Czech and Tagalog
Conclusions
Successfully able to build corpora for minority languages (Slovenian, Croatian, Czech, Tagalog) using Web search engines
Not sensitive to initial “seed” documents
System and Corpora are/will be available at www.cs.cmu.edu/~TextLearning/CorpusBuilder
Ideas for Future Work
Explore other Term-Selection methods
From Language specific corpus to Topic Specific corpus as an alternative to focused spidering
Finding documents matching a user profile – Personal Agent