The method 1, wherein providing the database comprises associating the map objects with respective data layers, and wherein identifying the two or more matched map objects comprises searching for the two or more matched map objects only within {HEAD ~ a subset} of {TAIL ~ the data layers} 
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The method 1 , wherein providing the database comprises associating the map objects with respective data layers , and wherein identifying the two or more matched map objects comprises searching for the two or more matched map objects only within { HEAD ~ a subset } of { TAIL ~ the data layers }
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