Instead of using optics for the entire retrieval process, they use it to guide a second, electronic (and error-free) search of a large, conventionally stored database.

ECONOMIST: Optical recognition

The person who typed in the search might get an error page and might have problems accessing Google or other sites for some period after, even for non-sensitive searches.

MSN: An explanation of Google's moves in China

For Jupiter analyst Olivier Beauvillain, Yahoo's initial decision to put its investment on search on hold was an error.

BBC: NEWS | Technology | Can Yahoo dominate next decade?

This uses a process of randomisation and trial-and-error (akin to mutation and selection in biological evolution) to search the vast number of possible microstructures to find the most suitable design for each subsection.

ECONOMIST: MONITOR

That settled, I hashed out the text for a link on the home page and a dozen error messages that would be displayed randomly if someone entered a query in the MentalPlex search box.

WSJ: Google: The Beginning

For example, using data on searches for trucks and SUVs to predict the monthly sales of motor vehicles reduces the average error by up to 18% compared with the predictions from a model that did not incorporate the search data.

ECONOMIST: Internet search data may be useful for forecasters