C-class flares, the weakest in scientists' three-tiered classification system, have few noticeable consequences.

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Some in the field have been frustrated by the classification system, which focuses on behavioral symptoms and not on chemical changes or brain abnormalities.

WSJ: Revised Psychiatric Manual Faces Mixed Reviews

Cannon was known as the "census taker in the sky, " and developed a stellar classification system that became the standard of the Harvard Observatory.

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With its new manual, the APA might instead have started taking steps toward a system of classification that, as in medicine, organizes disorders according to what we know about their natures and causes.

WSJ: DSM-5: A Manual Run Amok

The manual's classification system also has been a major factor in decisions involving grant funding and scientific publications.

WSJ: Revised Psychiatric Manual Faces Mixed Reviews

In 1851, American librarian Melvil Dewey, who devised the system of classification for library cataloguing, was born.

CNN: Tuesday,

These vehicles' front passenger airbags may not deploy in the event of a crash because of a possible problem with their occupant classification system, which gauges the size of a passenger and based on that whether an air bag should be deployed.

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This step moves us closer to meeting the recent Jobs Council recommendation to enable regulations to be searched by North American Industry Classification System (NAICS) codes, (NAICS is a standard used by Federal agencies in classifying industry).

WHITEHOUSE: Regulations.gov: Remaking Public Participation