Parallel Tools for Natural Language Processing Mark Brigham Melanie Goetz Andrew Hogue / March 16, 2004

Consider the sentence: “John ate the cookie on the table” We want to: –Tag the sentence with parts of speech –Group the words by phrase Sentence Parsing

… Context Free Grammars Recursive set of rules Defines what syntactic structure can be applied to a phrase or word Top-level rule S defines the sentence S→NP VP NP→Det N NP→NP PP VP→VP PP VP→V NP N→‘cookie’ N→‘table’ Det→‘the’ V→‘ate’

Context Free Grammars Applying a CFG to a sentence creates a parse-tree for that sentence

Context Free Grammars Top-down parse

Context Free Grammars Bottom-up parse Parallelizable!

Ambiguity More than one parse for a single sentence!

Parallelization Bottom-up rule application appropriate for parallel processing Ambiguous parses also parallelizable Long, complex sentences may be most interesting Proust?

Chart Parsing Create a matrix where entries correspond to words/phrases If there is a valid CFG parse of a phrase [i,j], add it to that matrix cell A cell [i,j] may only depend on other cells [m,n] where m < i and n < j.

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

John ate the cookie on the table John ate the cookie on the table

Other Tools Considering parallelizing other NLP tools Word-stemming: Multiple finite state automata applied to a single word in parallel Automated part-of-speech recognition on large corpora