Text data mining concerns the application of data mining (knowledge discovery in databases, KDD) to unstructured textual data. Our work focuses on using information extraction to first extract a structured database from a corpus of natural language texts and then discovering patterns in the resulting database using traditional KDD tools. It also concerns record linkage , a form of data-cleaning that identifies equivalent but textually distinct items in the extracted data prior to mining. It is also related to our research on natural language learning.