OW Sapphire/Emerald (and Ruby, below the others) reflect status levels on an individual oneWorld member airline. If you are AA Gold, you are also OW Ruby. If you are AA Platinum, you are also OW Sapphire. If you are AA Executive Platinum, you are also OW Emerald. The conversion from other airlines is similar in concept, though some don't have a level for all three OW levels. (For example, BA has no level that corresponds to OW Ruby.) There is no such thing as OW elite status independent of member airline elite status.

Each airline has its own rules for achieving status. On AA, it's earned on a calendar year basis, but they have a "soft landing" policy where you drop by at most one level each year even if you don't fly at all. (Someone earning EXP today will have at least some status until March 2014, over four years down the road.) Some airlines use the calendar year also, but do not have a "soft landing." Some do not have a fixed year, but base your year on when you signed up for their program or when you achieved a level of status. A few, Lufthansa's top level comes to mind, are based on a period longer than a year. And there's lifetime status, as mentioned - but not only on AA. Many airlines have some form of lifetime status, though AA is AFAIK the only one that bases it on total miles earned from all sources. The other ones with which I'm familiar base it on either actual miles flown (usually with a minimum per segment) or years holding earned status in the program.