Grey systems theory, probability theory, fuzzy systems
theory and rough set theory are known as four uncertain systems
scientific methodologies. After thirty years of development, grey
systems theory has formed its own disciplinary framework, whose
content includes grey philosophy, grey mathematics, processing and
technology systems of grey information, as well as grey systems
engineering. However, as a developing area of scientific
activities, a lot of theoretical contents are still imperfect and
awaiting further studies. The purpose of this paper is to acquaint
the readers with the development history, the main content and the
major challenges of grey system theory. It is our hope that this
paper could play the role of attracting the attention of the
international academic community to the theory
so that the development of this theory could be further promoted.