# Welcome to HEMDAG’s documentation!¶

HEMDAG package:

• implements several Hierarchical Ensemble Methods (HEMs) for Directed Acyclic Graphs (DAGs);
• reconciles flat predictions with the topology of the ontology;
• can enhance the predictions of virtually any flat learning methods by taking into account the hierarchical relationships between ontology classes;
• guarantees biologically meaningful predictions that always obey the true-path-rule, the biological and logical rule that governs the internal coherence of biomedical ontologies;
• is specifically designed for exploiting the hierarchical relationships of DAG-structured taxonomies, such as the Human Phenotype Ontology (HPO) or the Gene Ontology (GO), but can be safely applied to tree-structured taxonomies as well (e.g. FunCat), since trees are DAGs;
• scales nicely both in terms of the complexity of the taxonomy and in the cardinality of the examples;
• provides several utility functions to process and analyze graphs;
• provides several performance metrics to evaluate HEMs algorithms.