A RolapConnection uses one AggRule. If no name is specified, then
the AggRule which is marked as default==true is used (validation
fails if one and only one AggRule is not marked as the default).
An AggRule has manditory child elements for matching the
aggregate table names, aggregate table fact count column,
foreign key columns, the measure columns, and the hierarchy level
columns. These child elements can be specified as direct children
of an AggRule element or by reference to elements defined as a
pier to the AggRule (using references allows reuse of the child
elements and with one quick edit the reference to use can be
changed by changing the refid attribute value).