An unsupervised probabilistic learning framework for normalizing product records across different retailer Web sites is presented. Our framework decomposes the problem into two tasks to achieve the goal. The first task aims at extracting attribute values of products from different sites and normalizing them into appropriate reference attributes. This task is challenging because the set of reference attributes is unknown in advance. Besides, the layout formats are different in different Web sites. The second task is to conduct product record normalization aiming at identifying product records referring to the same reference product based on the results of the first task. We develop a graphical model for the generation of text fragments in Web pages to accomplish the two tasks. One characteristic of our model is that the product attributes to be extracted are not required to be specified in advance and an unlimited number of previously unseen product attributes can be handled. We compar...