How to Create a PHP Script for Decision Support System Using AHP Method
Decision support systems (DSS) are computer-based tools that help users make informed and rational choices among different alternatives. One of the most popular methods for DSS is the analytic hierarchy process (AHP), which is a multi-criteria decision making technique that uses pairwise comparisons to rank the alternatives based on their relative importance and preference.
In this article, we will show you how to create a PHP script for a simple DSS using AHP method. We will use an example of selecting the best laptop among four options based on three criteria: price, performance, and design. We will assume that you have some basic knowledge of PHP and HTML, and that you have installed a web server and a PHP interpreter on your computer.
Step 1: Define the Problem and the Alternatives
The first step in creating a DSS using AHP method is to define the problem and the alternatives. In our example, the problem is to select the best laptop among four options: A, B, C, and D. The alternatives are defined by their attributes, such as price, performance, and design. You can use any source of information to obtain these attributes, such as online reviews, specifications, or personal preferences.
For simplicity, we will use numerical values to represent the attributes of each alternative. The higher the value, the better the attribute. For example, a laptop with a price of 1000 has a better price than a laptop with a price of 1500. The table below shows the attributes of each alternative in our example.
Step 2: Define the Criteria and Their Weights
The next step in creating a DSS using AHP method is to define the criteria and their weights. The criteria are the factors that influence the decision making process, such as price, performance, and design in our example. The weights are the relative importance of each criterion in relation to the others. The higher the weight, the more important the criterion.
To determine the weights of each criterion, we need to use pairwise comparisons. Pairwise comparisons are a way of comparing two items at a time and expressing their relative preference using a numerical scale. For example, if we compare price and performance, we can say that price is equally important as performance (scale = 1), or that price is moderately more important than performance (scale = 3), or that price is extremely more important than performance (scale = 9), or any other value in between.
We can use a matrix to represent the pairwise comparisons of all criteria. The matrix has n rows and n columns, where n is the number of criteria. The diagonal elements are always 1, since each criterion is equally important as itself. The upper triangular elements are the pairwise comparisons of row criterion over column criterion, using the scale from 1 to 9. The lower triangular elements are the reciprocal values of the upper triangular elements, since if row criterion is x times more important than column criterion, then column criterion is 1/x times more important than row criterion.
The table below shows an example of a pairwise comparison matrix for three criteria: price, performance, and design. You can use any method to obtain these values, such as expert judgment, surveys, or personal preferences.