In their briefs, Google Spain and Google Inc.'s argument hinged on the meaning of "personal data" and "crawling." Crawling, as noted above, was the use of software programs to find multiple websites that responded to requests for information online These programs were configured to look for information on the Internet, according to a set of criteria that told them where to go and when." Once the relevant web pages bad been copied and collected, their content was analyzed and indexed." Google compared its search engine index to an index at the back of a textbook, in that it included information about words and their locations.