During the life cycle of a project it is sometimes necessary to extend a conformed hierarchy into a specific fact schema or conformed hierarchy.

For example, in the following figure there is an instance of conformed hierarchy 'Date', assuming that in a specific fact schema there is the need to model this conformed hierarchy adding informations about 'Quarter' and 'Semester'. If the designer changes the structure of the conformed hierarchy, these changes will be propagated in each fact schema that contains an instance of this conformed hierarchy

But if the designer puts informations about 'Quarter' and 'Semester' directly into the specific factschema, extending the conformed hierarchy instance instead of the conformed hierarchy 'master' , these changes will affect only the fact schema.