Table 1.

The concept of gray in gray theory model.

Occasion	Ash	White	Black
Information angle	Incomplete	Completely	Unknown
Superficially	Looming	Clear	Dark
Process perspective	Handover of old and new	Old	New
Nature angle	Various compositions	Simple	Confusion
Method angle	Sublation	Positive	Negative
Attitude angle	Tolerant	Strict	Indulgence
Results	Nonunique solution	Unique solution	No solution