A classification can be extended by adding more detailed concepts to it and defining hierarchical relationships between the new concepts and the classification. A classification and its extension can be managed by two separate organisations.
In order to achieve a deeper level of detail in ESCO, e.g. for specific economic sectors, the occupations and skills pillars of ESCO can be extended. This is useful for building sector-specific applications of higher accuracy, e.g. job-matching, workforce planning or career guidance tools for a specific economic sector.