18. The computer-implemented system of claim 16 , wherein the hidden attribute extractor is further adapted to extract hidden attributes using segmentation of text associated with the web pages, and using iterative pairwise alignment.
16. A computer-implemented system for stitching tables comprising: a computer; a non-transitory computer readable medium in data communication with the computer and storing instructions executable by the computer and that define: a stitchable table identifier within the computer and adapted to receive extracted tables from one or more web pages, wherein each of the one or more web pages comprise one or more corresponding text portions that are separate from the two or more tables, and compare the headers of the two or more tables and determine semantic equivalence of headers based on the comparison, and determine the extracted tables to be stitchable tables based on the headers of the two or more tables being determined as semantically equivalent; a hidden attribute extractor within the computer and adapted to receive the two or more stitchable tables and determine, for each of the stitchable tables, the corresponding text portions of the one or more web pages from which the stitchable tables are extracted, and extract, from the determined corresponding text portions, hidden attributes that are related to content included in the two or more stitchable tables; and a table stitcher within the computer and adapted to create a union table by joining the stitchable tables, and add the hidden attributes to the union table in one or more new columns within the union table; and a non-transitory storage adapted to store the extracted tables and the union table.