A Wordnet from the Ground Up

3.4. Measures of Semantic Relatedness 773.4.5 Benefits for wordnet constructionOur aim in MSR extraction was ultimately to use MSR as the basic knowledge sourcein semi-automatically expanding plWordNet with new synsets and relation instances.We planned to obtain material for new synsets by clustering target LUs by MSRproducedvalues. We discuss the experiments next, in Section 3.5. We also hoped tofind on the MSRlist (x,k) lists new instances of wordnet relations between LUs presentin plWordNet and new LUs, as well among new LUs. We assumed manual verificationof the results. An MSR was constructed for a set of one-word and two-word nominalLUs 16 including all LUs already present in the core plWordNet, as well a set of LUsplanned as the basis for expansion. The drawbacks of a pure corpus approach, discussedin Section 2.4, made us take a more dictionary-based approach in defining the lemmalist for the expansion of plWordNet. In the end, 13285 nominal LUs have been selectedfor extracting an MSR for nominals:• 5340 nominal lemmas described in the core plWordNet,• additional lemmas (further on referred to as new lemmas):– nominal lemmas acquired from a small Polish-English dictionary(Piotrowski and Saloni, 1999),– two-word LUs from a general dictionary of Polish (PWN, 2007),– the lemmas that occur over 1000 times in the largest available corpus ofPolish, IPIC (Przepiórkowski, 2004),The small Polish-English dictionary (Piotrowski and Saloni, 1999) was used as themain source, because its small size makes its entries close to the core of the Polishvocabulary.First experiments on MSR extraction had been performed only on IPIC (Piaseckiand Broda, 2007, Piasecki et al., 2007a,b). Later, when we collected other corpora, weobserved a correlation between an increase in WBST+H and the increasing size of theoverall corpus used. The final version of the nominal MSR has been extracted fromthree corpora:• IPIC (including about 254 million tokens) (Przepiórkowski, 2004) (it is not balancedbut it covers a variety of genres: literature, poetry, newspapers, legal texts,stenographic parliamentary records and scientific texts);• a corpus of the electronic edition of a Polish newspaper Rzeczpospolita fromJanuary 1993 to March 2002 (about 113 million tokens) (Rzeczpospolita, 2008);16 We were limited to at most two-word LUs by the technology of the extraction of multiword expressionwe had developed (Broda et al., 2008).