A Survey on Tree Aggregation
Saloni Kwatra, Vicenç Torra · 2021
The research dedicated to the aggregation of classification trees and general trees (hierarchical structure of objects) has made enormous progress in the past decade. The problem statement for aggregation of classification trees or general trees is as follows: Given k classification or general trees for a set of objects, we aim to build a consensus tree (classification or general). That is, a representative tree for the given trees. In this paper, we explore different perspectives for the motivation to construct a single tree from multiple trees given by researchers. The survey presents the approaches for the aggregation of both the classification trees as well as general trees. We bifurcate our study of the aggregation approaches into two categories: Selecting a single tree from multiple trees and merging trees. We will discuss these categories and the aggregation approaches under these categories in the paper comprehensively. We also discuss the privacy aspects of tree aggregation approaches and the possible directions for new research like using the technique of aggregating decision trees in the field of Federated Learning, which is a booming topic.