The field of complexity is becoming increasingly important
in science and engineering. It transcends traditional
disciplines as all fields of natural science, engineering,
and social science must deal with complexity. However,
each sub-field of science and engineering has defined
and viewed complexity in different ways to satisfy its
immediate needs due to the lack of unifying concepts or
theories. Often various aspects of complex systems in
different fields are treated ad hoc without a clear definition
of "complexity" rather than creating a fundamental
approach to complexity. Ultimately, the field of complexity
may emerge as a unified discipline using a common set of
principles and theories but with a different knowledge
base and constraints. To achieve this goal, we have to
define 'complexity' in an unambiguous manner.