A Hybrid Grey Based KOHONEN Model and Biogeography-Based Optimization for Project Portfolio Selection

Table 3

The variables and parameters of the mathematical model of project portfolio selection.

Variables of the model	Description
One-zero variable	1 is assigned to the ith project and 0 otherwise
	All of the proposed projects
	Risk of every project
	The required time for completion of each project
	The rank of each project
	The overall resources required
	The resources required for the ith project
	Completion time of the ith project
Research objectives:
(1) minimizing the risk of portfolio
(2) maximizing the rank of each portfolio
Limitations:
(1) resources limitation for completion of the projects
(2) time limitation for the completion of each project
(3) binding limitations for implementation of the project
(4) binding limitations for implementation of the project