“…That implies that as the complexity of typical web documents increases, information extractors have to analyze more and more irrelevant regions, which has an impact on both efficiency and effectiveness [84], [163], [175]. This has motivated a number of authors to work on region extractors as a means to relieve information extractors from the burden of analyzing many regions of a web document that do not contain any relevant information [19], [23], [24], [53], [84], [97], [100], [114], [125], [141], [163], [169], [179], [180]. The difference between information extractors and region extractors is that the former focus on extracting and structuring data records and their attributes, whereas the latter focus on identifying the HTML fragments that contain this information.…”