Sorry for the confusion. They are used for "merging" scraped data from various sources, not in the scraping process itself. For example, they help in figuring o

Sorry for the confusion. They are used for "merging" scraped data from various sources, not in the scraping process itself. For example, they help in figuring out if similar-sounding listings on related websites refer to the same "thing". If interested, take a look at this (and related) papers: http://www.cs.ubc.ca/~murphyk/Papers/kv-kdd14.pdf http://www.cs.ubc.ca/~murphyk/Papers/kv-kdd14.pdf