| dc.description.abstract | In the development of rough set theory, many different interpretations and formulations
have been proposed and studied. One can classify the studies of rough
sets into algebraic and constructive approaches. While algebraic studies focus on
the axiomatization of rough set algebras, the constructive studies concern with the
construction of rough set algebras from other well known mathematical concepts and
structures. The constructive approaches are particularly useful in the real applications
of rough set theory. The main objective of this thesis to provide a systematic
review existing works on constructive approaches and to present some additional results.
Both constructive and algebraic approaches are first discussed with respect to
the classical rough set model. In particular, three equivalent constructive definitions
of rough set approximation operators are examined. They are the element based, the
equivalence class based, and the subsystem based definitions. Based on the element
based and subsystem based definitions, generalized rough set models are reviewed and
summarized. One can extend the element based definition by using any binary relations
instead of equivalence relations in the classical rough set model. Many classes
of rough set models can be established based on the properties of binary relations.
The subsystem based definition can be extended in the set-theoretical setting, which
leads to rough set models based on Pawlak approximation space, topological space,
and closure system. Finally, the connections between the algebraic studies, relation
based, and subsystem based formulations are established. | |
