1. A method for automatically constructing wrappers across a plurality of domains, executed by a processor, the method comprising: creating a first wrapper in a first domain in the plurality of domains using a first set of training data, the first set of training data created from a subset of documents in the first domain; applying the first wrapper to each page in the first domain to extract additional training data; combining the first set of training data with the additional training data to generate a first target string; searching domains in the plurality of domains other than the first domain to determine if any domain in the plurality of domains other than the first domain comprises at least one document having at least one portion of the first target string; and creating a second wrapper for at least one of the other domains in the plurality of domains from the first target string.