Investigating the concepts of entity and identity in the cataloguing field constitutes the starting point of this work. Little explored in their most profound meaning and cataloguing application, the two concepts have never been analyzed in relation to the identification and modeling of objects in the GLAM domain. This activity is not simple, especially where the diversity of profiles makes the entity a multifaceted object, with boundaries that are only sometimes clear and defined, often fluid, and, therefore, difficult to fix. The need to identify the entities that make up the rich bibliographic universe leads us to hypothesize another way of looking at cataloguing: entity modeling presents itself as the third generational step in the management of bibliographic data, imposing or requiring a change of perspective in the processing of information but also in the language of formalization of the same.