As the special moduel to view a disease, based on the numerous practical experience, syndrome is a pathological model deduced from all the collected manifestations of a disorder by the ancient people who dealt with connection between different parts inside and outside the human body according to the relevent life phenomena.

This paper aims at a "boundary" result more general than both Segerberg s theorem and Nagle s theorem: all modal logics of finite depth have the finite model property, no matter they are transitive or not.

"canonical" and "finite model property" are different conceptions,which are relevant to the system s completeness.

Finally,an interval stress-strength interference model with model uncertainty was developed with.