3.2 AHP-based Evaluation for DPSIR Model
In DPSIR model,many factors are involved in each stage and these factors are associated with some other objective ones with different impacts.In order to quantitatively evaluate the stages of DPSIR model,we take AHP method for evaluation.The evaluation system as shown in the Table 1.
Table 1 The evaluation system
The whole process can be divided into the following three steps：
Step 1 Standardize the data of different dimensions for comprehensive evaluation of all the factors.
Effect attribute indicator：
Cost attribute indicator：
Of which C is an index value after normalization while a min and a max are respectively the minimum and the maximum.
Step 2 Define the weights of each factor.
We evaluate each factor according to the relative importance of factors(Table 2)acknowledged in the United Nations Conference[2,3].
Table 2 The relative importance of factors
Thus,W Di,W Pi,W Si,W Ii,W Ri are respectively obtained for the evaluation of primary indicators D,P,S,I,R.
As the same,W Di,W Pi,W Si,W Ii,W Ri are respectively obtained for the evaluation of secondary indicators Di,Pi,Si,Ii,Ri.
Step 3 Calculate the final score of comprehensive evaluation.
For secondary indicators Di,Pi,Si,Ii,Ri：
For primary indicators D,P,S,I,R：
Of which X can represent one of D,P,S,I,R.M and N are respectively the number of evaluation factors of primary indicators and secondary indicators.
In AHP,the weights of factors are the key and different weights may lead to different results.In order to ensure the reliability of weights f we define according to the importance relativity of indicators acknowledged in United Nations Conference.