Categories are equivalence classes: sets or groups of things or abstract entities that we treat the same.
The size of the equivalence class is determined by the properties or characteristics we consider.
We can describe category abstraction in terms of a hierarchy of superordinate, basic, and subordinate category levels.
Any particular collection of resources can be organized using a combination of intrinsic, extrinsic, static and dynamic resource properties.
Broader or coarse-grained categories increase recall, but lower precision.
Classical categories can be defined precisely with just a few necessary and sufficient properties.
An important implication of necessary and sufficient category definition is that every member of the category is an equally good member or example of the category.
The most conceptually simple and straightforward implementation of categories in technologies for organizing systems adopts the classical view of categories based on necessary and sufficient features.
Any collection of resources with sortable identifiers (alphabetic or numeric) as an associated property can benefit from using sorting order as an organizing ...