An improved visualization-based approach for project portfolio selection

Highlights

• We present a visualization approach for a single-criterium optimization problem.

• We propose an interactive dashboard of costs, risks and project allocation in time.

• We propose an interactive chart of man-hour data.

• We present a new cluster-based layout for timelines with draggable events.

Abstract

We propose a 2-step interactive approach for solving a project portfolio selection problem as a single-criterium optimization problem. Our approach innovates by using two coordinated charts: an interactive project timeline with drag-and-drop functionalities for project reallocation in time; and an interactive cost and risk chart that combines line charts and bar charts in order to present multidimensional time-based datasets. We also use bar charts related to the allocation of man-hour resources. These functionalities enable users to refine the model that is fed into optimization software in order to achieve results that better correspond to their expectations. We discuss results of a heuristic-based usability evaluation of our prototype, its use in real scenarios, and present preliminary positive feedback from users.

Introduction

Multi-objective optimization approaches model the entities of a problem as well as preferences and requirements provided by decision makers in order to calculate one or more non-dominated optimized solutions that make the Pareto frontier for the problem. However, models may not capture entirely all user requirements and preferences, and so they produce optimum solutions in terms of the modeled problem only, instead of dealing with the real world problem. Interactive approaches may complement this scenario (Fisher, 1985). In the Project Portfolio Selection (PPS) problem, given a set of projects, an optimization software must determine when each project begins, in order to optimize technical criteria, such as reducing the portfolio makespan or determining minimum funding necessities. After that, some approaches use interactive visualization techniques to present these solutions to decision makers, in order to enable them to further explore the solution set.

In this work, we show how single-objective optimization problems may also benefit from interactive approaches. A single-objective optimization problem aims to construct a single best solution of a problem, i.e., it seeks the best value of a single objective function (Bandyopadhyay & Saha, 2013). Enabling decision makers to modify a solution helps them to adjust their preferences in a neighborhood of a proposed best solution. Besides, our visualization-based approach, based on interactive coordinated graphics, enables users to explore alternative solutions in an incremental, reversible and easy-to-learn way. Our main contributions are:

• An interactive visualization approach for insertion of decision maker's preferences into the optimization problem;

• An interactive coordinated view of costs, risks, man-hours and individual projects allocation in time, based on timelines, barcharts, and line charts.

• An alternative layout algorithm for timelines, which allows for dragging events (in this context, portfolio projects) by increasing the interaction area.

The next sections are organized as follows. First, we review interactive approaches and visualization solutions, followed by a more precise description of the PPS we have at hand. After that, we explain our visualization-based methodology for dealing with our single-objective PPS problem, which includes user, data, tasks, and insights characterizations, as well as the definition of interactive charts that provide such insights to users. Then we present the results of a heuristic evaluation of usability. Besides, we show the use of our approach in a real world scenario, and report on preliminary user opinions about it. Lastly, we conclude and present ideas for future work. It is worth noting that this paper is an extended version of another published work of our research team (Silva et al. 2016b).