I like this page for well understanding the fuzzy logic rules:

http://www.cs.cmu.edu/Groups/AI/html/faqs/ai/fuzzy/part1/faq.html

There you can find the methods for the construction of fuzzy scales. On automatic procedures aimed to extraction of information from multiple texts written about the same topic, fuzzy logic is very usefull for clasify the extracted information. For example, by positive or negative oppinions about that topic or other. On more complex studies you can apply by example the Osgood Scale, it permits (under the fuzzy rules) to compare positions and/or predicates about more than one topic on a sample of documents automaticaly analysed.