《Table 11 The performance of landform value extraction for the descriptive text of soil profiles wit

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《Automatic extraction and structuration of soil–environment relationship information from soil survey reports》

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1) The P，R and F1 denote separately precision，recall and F1-measure value.2) The Wn，Pn and Kn stand for word，part-of-speech，K value，and their context features in window sizes n.

The above process was accomplished mainly through Chinese word segmentation（e.g.，“20°以上” （over 20degree）is segmented to“20，°，以上（over）”） ，part-of-speech tagging（e.g.，“20[number]，°[quantifier]”），prefix and suffix matching（e.g.，“以上 （over）[suffix]”） and rule matching（e.g.，“20[number]+°[quantifier]+以上 （over）[suffix]”matches with the rule:“number+quantifier+suffix”） .Chinese word segmentation and part-of-speech tagging can be carried out with free software tools such as NLTK（http://www.nltk.org），Stanford NLP（http://stanfordnlp.github.io/CoreNLP），and LTP（http://github.com/HIT-SCIR/ltp）.Prefix and suffix matching need a dictionary of prefixes and suffixes.The establishment of a prefix and suffix dictionary is as follows:1) Manually summarize the prefix and suffix words that appear in the variable values in terms of semantics and 2) expand them using the synonym dictionary.Then，combine the adjacent tags，including the prefix，number，punctuation，quantifier and suffix，into a sequence（e.g.，“20[number]，°[quantifier]，以上 （over）[suffix]”is combined into“number+quantifier+suffix”） and extract the potential variable value by matching the sequence with rules in a rule base.To get diverse types of variable values，a rule base needs to be established.The rule base can be generalized manually according to variable value instances.Examples of the rules are shown in Table 1.Several rules may be matched in the base；therefore，among the potential variable values，the best variable value remains to be picked out.The maximum matching method was used to start the match from the left side and select the longest match in a match set.Ultimately，the longest one was taken as the most suitable soil variable value.