A Wordnet from the Ground Up

166 Chapter 5. Polish WordNet Today and TomorrowThe expansion process was therefore slightly biased towards a data driven approach 2 .Such a bias is not necessarily a drawback, however, because – assuming moderateinfluence of the linguists’ decisions – the resulting resource represents a structure oflexico-semantic relations implicitly present in the language data.The operation of pattern-based methods was also limited to the list of 15096 selectedlemmas – its late version supplemented by the frequent lemmas from the jointcorpus. (Support for this design decision comes from preliminary experiments, inwhich we applied pattern-based methods to an unrestricted, full list of lemmas collectedfrom the joint corpus. In the absence of any restrictions, there were very manyextracted instances, at the cost of much lower precision.)An improvement in the number of dictionary lemmas covered can naturally behad if there is a larger and better balanced corpus to cover more domains and moreexamples per word sense. This is not a realistic wish, but there still is much room insemantic extraction for increased use of what is present in texts. For example, MSRconstruction could easily benefit from a deeper analysis of the lexico-syntactic structureafforded by a syntactic analyser.We only applied the semi-automatic process to nominal lemmas. The presentversion WNW strongly depends on the hypernymy structure, rich for nouns, but quitelimited for verbs and very rare for adjectives. There simply was no basis for theidentification of attachment areas. (In the future versions of WNW, we plan to usemore relation types in generating suggestions.) Also, few lexico-syntactic patternswork for verbs. It is a serious open problem to find effective use of information comingfrom single occurrences of verbal and adjectival lemmas in a style of pattern-basedapproaches.Here is how we have organised around WNW the process of expanding plWordNet.1. We collected and morpho-syntactically preprocessed a large corpus ( Section 3.4.3).2. From the corpus, we extracted data sets describing lexico-semantic relations; weapplied all constructed and experimentally verified automated extraction tools:the Measure of Semantic Relatedness MSR GRW F , manual patterns and Estratto(Section 4.3).3. A classifier for lexico-semantic relation (Section 4.5.1) was trained on the thencurrentstate of the wordnet and the data sets from the previous step.4. New lemmas were clustered using MSR GRW F and an off-the-shelf clusteringtool; we applied the Cluto package (Karypis, 2002).2 It is important to note that the ultimate decisions belonged to linguists, who could also freely addrelation instances not suggested by WNW.