To put this in terms of praxis, bulk_extractor (a digital forensics tool used to find personally identifiable information on a disk image <a href="http://www.forensicswiki.org/wiki/Bulk_extractor)">http://www.forensicswiki.org/wiki/Bulk_extractor)</a> relies on context in order to identify critical information such as credit card numbers, social security numbers, email addresses, etc.