Extracting knowledge or producing summaries from unstructured text are ever more important applications, in view of the deluge of documents issuing forth from news media, organizations of every sort, and individuals. This unceasing stream of information makes it difficult to gain an overview of the items relevant to some particular purpose, such as basic data about individuals, organizations and consumer products, or the particulars of accidents, earthquakes, crimes, company take-overs, product maintenance and repair activities, medical research results, and so on.