In a Board database relationships are always hierarchical: a relationship defines a many-to-1 relationship between two entities that we therefore refer to as the parent entity and the child entity. For example, State and City clearly are parent and child entities: a city can only be in one state and a state includes several cities.
Entities and hierarchies provide views on InfoCubes (usually numerical data) at various aggregation levels, for example, Sales by State or by City. Two entities, a parent and a child are also often referred to as less aggregate or more aggregate entities: a view at a parent entity level is the aggregation of the data from the child entity level.
Board supports multiple parallel hierarchies meaning that an entity can have multiple roll-up paths. For example, the Customer entity could roll-up into the City and State (this is the first branch) and independently roll-up into Salesman and Area Manager entities (this is another branch) and into Channel (this is a third branch). Hierarchies are also referred to as trees. The following illustration shows a Customer hierarchy made of three parallel branches.
Building the hierarchies is one of the key steps of building the multidimensional model. The hierarchies must provide a truthful representation of the business model or the organization you are modeling. A relationship between two entities should only be defined if there is an organizational rule or some kind of constraint that enforces it.If we look at the State and City entities, it appears quite obvious that a hierarchical relationship should be defined between the most aggregate, State (the parent) and the less aggregate City entity (the child). Sometimes the choice is not so obvious; let’s consider for example the entities Customer and Salesman. Defining the hierarchical relationship CustomeràSalesman, implies that a Customer can only be related to a single Salesman. Only if this is an organizational rule is it then appropriate to define a relationship CustomeràSalesman, otherwise, if a salesman can visit (or sell to) any customer, then the two entities should remain unrelated.
To access the relationships transaction, click the relationships icon of the ribbon bar as illustrated,
The relationships transaction shows the list of entities of the database in the first column and the more aggregate entities (parents) to its right on the same row.
It is also possible to view and edit relationships using the Graphical View mode which represents relationships in a hierarchical tree.
