1. A method for extraction of suggestions for improvement comprising: providing a structured terminology for a topic, the structured terminology including a set of semantic classes, each of a plurality of the semantic classes including a finite set of terms; providing a thesaurus of terms relating to suggestions of improvement; receiving a corpus of text documents, each document comprising a text string in a natural language; labeling text elements in the text strings which are instances of terms in the structured terminology with the corresponding semantic class; labeling text elements in the text strings which are instances of terms in the thesaurus; with a processor, applying a set of patterns to the labeled text strings to identify suggestions of improvement expressions, the patterns each defining a syntactic relation between text elements, the patterns including: for each of the semantic classes in the set, at least one pattern which specifies a syntactic relation in which one of the text elements in the relation is labeled as an instance of the semantic class, and wherein at least one of the patterns specifies a syntactic relation in which one of the text elements in the relation is labeled as an instance of one of the terms in the thesaurus; and outputting a set of suggestions for improvements based on the identified suggestions of improvement expressions.