Characters are central to narrative theory but remain under-specified in computational work, where they are often reduced to clusters of words or vectors. We propose an operationalizable ontology of characterization that bridges narratological theory and NLP. From BERT-based clustering of character descriptions, we derive 17 classes of attributes (actions, emotions, traits, relations, possessions, etc.), validated through manual annotation (
$k = 0.77$) and automatic classification (64% accuracy vs. 12% baseline). Applied to character similarity tasks for French fiction, our framework outperforms existing models. By aligning narratological insights with computational methods, we move toward a representation of fictional characters as structured, comparable entities for large-scale literary analysis.