A method for generating marks when displaying data, such as the results of a query across a database. The method is preferably used in conjunction with a dataset whose fields comprise a plurality of levels. A visual plot is constructed based on a specification. A first level from the plurality of levels is represented by a first component of the visual plot. A second level from the plurality of levels is represented by a second component of the visual plot. The dataset is optionally queried to retrieve data in accordance with the specification. The visual plot is populated with the retrieved data in accordance with the specification.