14. The apparatus of claim 13 , wherein a second tree level of the attribute category tree data structure beneath the first level of the attribute category tree data structure is reserved for the category numerical data and the third tree level of the attribute category tree data structure beneath the first and second levels of the attribute category tree data structure is reserved for the category textual data.
13. The apparatus of claim 8 , wherein the first tree level of tree data is reserved for non-numerical category image data; and the lower tree levels are reserved for category numerical data and category textual data.