A Wordnet from the Ground Up

4.5. Hybrid Combinations 133fers from MSR GRW F discussed earlier (Section 3.4) only in the transformation appliedand in a slightly lower accuracy. A detailed presentation of the applied MSR RW F canbe found in (Piasecki et al., 2007b, Broda et al., 2008).The second phase begins with the extraction, for the given LU u, of a list S ofk LUs most semantically related to u, denoted MSRlist (u,k) . Any value of k will do,but we noticed that, for the MSR types we used, the percentage of LUs in a wordnetrelation to u begins to deteriorate around k = 20. Next, we need a classifier to selecta subset of S that includes near-synonyms and close hypernyms of u.Instead of using frequencies of lexico-syntactic features collected from a corpusdirectly as attributes in learning the classifier, we want to identify a set of complexfeatures that can give clues on the relation between two LUs. We intend to applya kind of knowledge-based, partially linguistically-motivated, transformation of theinitial feature space into a new space of reduced complexity: fewer features and maybecondensed information on the LU relations of interest. For a pair of LUs, the valuesof attributes are calculated prior to training or testing. This is done via co-incidencematrices constructed from large corpora. We generally work with the same matricesas in the MSR RW F construction.In search for attributes, we drew on clues which can deliver information concerningthe specificity of compared nouns, the extent to which they mutually share lexicosyntacticfeatures, topic contexts in which they occur together and, last but not least,the value of their semantic relatedness. We now present the complete list of attributesused (a and b are noun LUs):1. semantic relatedness MSR(a, b) – the value returned by an MSR RW F ,2. co-ordination – the frequency of a’s and b’s co-occurrence in the same coordinatenoun phrase,3. modification by genitive – the frequency of a’s modification by b in the genitiveform,4. genitive modifier – the frequency of b’s modification by a in the genitive form,5. precision of adjectival features – the precision of repeating b’s adjectival featuresby the set of a’s features (for the calculation method, see formula 4.10 below),6. recall of adjectival features – the recall of repeating b’s adjectival features bythe set of a’s features (for details, see formula 4.11),7. precision of modification by genitive – the precision of repeating b’s features,which express modification by a specific noun in genitive, by the similar featuresof a (the calculation method is similar to that in formula 4.10),