(1) In this paper, it is discussed that non-central hole rotors essentialness and its advantage through studying the reason of adopting central hole rotor and its disadvantage.

(2) This paper builds game model among enterprises to study essentialness of imposing environmental tax based on game theory.

(3) Firstly, based on DLIO and the summarization of metadata, this paper illustrates the organization structure of DL's information resources, the essentialness of metadata's application in DLIO.

(4) The "Reform Program for Basic Curriculums(Trial)" emphasizes: "pedagogy is the unify of the teacher's teaching and student's learning which is the essentialness of the communication and interaction.

(5) The last part is about the disadvantages of litigation contract, and prove the essentialness for setting up some districting measures on litigation contract.

(6) In the fourth part, it is demonstrated that the reality and essentialness of the limited applied mediation system. It is analysed that the advantages and disadvantages of the system.