1. A computer-implemented method of defining object classes, comprising: on a computer, executing the method of: programming the computer with a browser-based classification editor having a first tier functionality and a second tier functionality; wherein said first tier functionality is operable to enable a user of said computer to create a new class having a first group; select and associate one or more attributes with said first group; and define and modify one or more conditions to said first group, wherein said first group comprises objects having said one or more attributes that meet at least one of said one or more conditions; and wherein said second tier functionality is operable to enable said user to manipulate an expression comprising said first group.