UML notation is assumed to be independent from any software modeling methodology. The existing methodologies support the creation of the final system model, but they do not care about the formal documentation of the reasoning process; the associations between the elements belonging to different types of UML diagrams are remembered either as informal documentation out-side the UML model or are forgotten. Described in the paper Vertical Relations try to fill this gap, and allow to look at the use of timing diagrams from the new, more complex, perspective. Usefulness of Virtual Relations in evaluation of the timing properties of the Data Warehouse Reporting systems is presented.