Attributes and Metrics are the objects we need to design and creating prior to building the reports. The drilling option between attributes and between different levels of an attribute in a hierarchy depends on teh relation we setup in the microstrategy architect.
There are 2 types of hierarchies, System hierarchy and User hierarchy (Picture courtesy from Microstrategy knowledge resource)
Hierarchies represent a set of attributes with paths between them. The System Hierarchy contains the true relationships (i.e., parent-child) between all the attributes in the schema. The System Hierarchy is automatically defined when attributes are created and their relationships to related attributes are specified. MicroStrategy Architect provides a unique abstraction of hierarchies above the System Hierarchy called User Hierarchies, which can contain an arbitrary number of attributes and paths between them. These User Hierarchies allow users to browse through the data and drill as required by business needs, as opposed to how the data is physically stored in the data source.