Model Subsetting
In some circumstances, only a subset of a model is available. These include when users do not have sufficient security permissions, when there are missing items in the physical model, when the model is derived from another model, or when the designer explicitly created a model subset.
When only a subset is available, missing items from the semantic model can affect other items within the model. For example, dependent items within the model are treated as if they have been removed from the model as well. If a reference is mandatory, for example, when specifying the Binding or RelatedRole elements, the referencing ModelItem element is treated as missing. Similarly, the innermost optional property, for example the Inheritance element, is treated as empty. References in queries to missing items generate a warning instead of an error, and the innermost containing detail, group, hierarchy, measure, measure group or subtotal set is omitted from the query. In the event a base entity is missing or all groups and all measures are omitted, the query fails.
Exceptions for Expressions
Attributes that the user has permission to see are not removed from the report model just because the expression is excluded. Instead, only the expression is removed from the report model. For aggregate attributes, this forces the attribute to be non-transitive and non-decomposable.
Attributes in a requested perspective are not removed from the user model when the components of the expression are excluded from the perspective. Instead, those components of the expression are included in the user model but marked as hidden.