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What is a national corpus
Primary objective of a national corpus is to provide linguists with a tool to investigate a language in the diversity of types of texts through making complex lexical grammatical queries.
The corpus allows to investigate various linguistic phenomena by observing the possible range of contexts in which they occur.
Examples of searchable corpora online
British National Corpus
Russian National Corpus
Eastern Armenian National Corpus
Czech National Corpus
To show just one example:Eastern Armenian National Corpus
• about 90 million tokens • powerful search engine for making complex lexical morphological queries • a diachronic corpus covering SEA texts from the mid-19th century to the present • both written discourse and oral discourse • open access
A national corpus is a large-scale, linguistically diversified and balanced collection of texts provided with a flexible search engine.
How large?
RNC 150 mlnBNC 100 mlnEANC 90 mln
Essentially, depends on the type of research envisaged
How diversified?
As diversified as practicable
EANC – extension of the press subcorpus to cover early Armenian press, soon to cover internet forums
RNC – effort to cover snail mail and electronic communication
EANC: subcorpus form
How balanced?
Balance is a vague notion…
At least not disproportionate – less poetry than prose etc. Even a disbalanced corpus can be balanced by creating predefined subcorpora.
As an example: EANC
Written discourse # tokens % EANC # of docs
Fiction
prose: novel 23 487 427 32,0% 287
prose: story 5 203 507 7,1% 104
prose: play 1 407 344 1,9% 46
prose subtotal 30 098 278 41,0% 437
poetry 2 392 710 3,3% 106
Press 22 471 921 30,6% 3895
Nonfiction
science 13 354 755 18,2% 109
essays, memoirs, official, religious 3 894 015 5,3% 320
Written discourse total 72 211 679 98,5% 4 867
Multicomponent corpora
Oral subcorpus (RNC, BNC, EANC)Dialectal subcropus (RNC)Poetic subcropus (RNC)Educational subcorpus (RNC)…
Library or corpus?
• electronic library is intended for readers
• corpus is intended for researchers
Difference in target audience and intended usage
Implied differences:
corpus must be able to respond to queries
library have major problems related to copyright
Technical requirement: reasonable expectation time
Functional requirement: complex queries
• you can not parse texts as you go (on flight)
texts need to contain mark up
• in large corpora, you can not simply search the markup
you have to index files, create datafiles and use special search algorythms
Parsing
Сlassification of inflectional types needs to be as exhaustive and formal as a logical calculus.
Parser creates a list of endings and a list of stems; when parsing a wordform, it tries to match the ending of the word with an ending in the list, then tries to match the rest with the stem, and checks whether this ending is allowed to be added to this stem.
• wordlist
• inflection type attributed to its each item
Parsing
•recent loanwords •neologisms•elements of code-
switching•abbreviations•proper names •technical terms
•distorted spellings•cases of inflectional variance
not included into the wordlist•scanning errors•typos and misspellings in the
original texts
Some tokens are not recognized at all; these tokens can not be searched by means of lexical or grammatical queries.
Parsing
Some tokens receive several analyses.
The actual applicability of these analyses depend on the context and may not be evaluated by the parser.
# of analyses Comment Fiction Science PressOther
WrittenOral
DiscourseEANC Total
1 unambiguous 73,9% 65,9% 70,4% 68,0% 63,0% 70,9%
2 ambiguous (homonimous) 15,4% 9,8% 12,4% 12,3% 14,1% 13,2%
3 ambiguous (homonimous) 2,7% 2,0% 1,9% 3,8% 2,4% 2,3%
4 - 7 ambiguous (homonimous) 1,4% 1,8% 1,8% 1,6% 1,5% 1,6%
Subtotal ambiguous 19,5% 13,7% 16,0% 17,7% 18,0% 17,1%
1? hypothetic (not in dictionary) 0,0% 1,3% 0,6% 0,7% 0,2% 0,5%
0 not recognized 6,2% 12,8% 9,9% 8,0% 13,9% 8,9%
Special tokens: Cyrillic, Latin, digits 0,3% 6,3% 3,1% 5,6% 4,9% 2,6%
Total 100% 100% 100% 100% 100% 100%
Search Functionality
Once again: the Corpus allows to investigate various linguistic phenomena by observing the range of contexts in which they occur.
• token queries
• context queries
• subcorpus queries
Search Functionality
Simple token queries:
• lexeme search
• wordform search
• gram search
Combined token queries:
• lexeme + gram search
Search Functionality
Additional and advanced options for token queries:
• case-sensitivity
• punctuation marks
• position in the sentence
• wildcard queries
• logical functions
• negated features
Search Functionality
Context queries: a combination of several token queries
• search for tokens at a specified distance
• search for tokens within one sentence
• search for tokens in adjacent sentences
• increasing the number of tokens ad infinitum
Search Functionality
Subcorpus selection: searching in a specified type of texts only
• search within a specific period of time
• search in texts of specified authors
• search in specified genres/types of texts
Search Functionality
Working with the results
• expanding the context
• pop-up grammar
• sort by…
Extras
• Translations (EANC)• Disambiguation (RNC)• Electronic library (EANC)• Syntactic markup• Statistics (RNC?)
Possible applications
Linguistics(corpus-based grammars projects under way) Education (www.studiorum.ruscorpora.ru to appear) Normative linguistics Literature and culture studies etc.