Hierarchy exception aggregations NGA and HGA are special aggregation rules for hierarchies with postable nodes. Postable nodes are hierarchy nodes that do not simply aggregate their child nodes but also have a value of their own that is added to the aggregation. It is possible to display the own value of a postable node as the child of this node so that the display corresponds to that of a normal hierarchy.
In the following example there is a normal hierarchy node (node 1) and a postable node below it with a value part (page 1) of its own. Page 1 can be displayed a the child of the postable node. Apart from this the postable node has an actual child (page 2). The following graphic shows the result of an aggregation of type SUM.
If output aggregation NGA is applied to key figure 1, this produces the result that the postable node only has the value of its own value part, that is, from page 1. The node on a higher level also only includes this value part so that node 1 of the example above also displays the value of page 1. This means that NGA ensures that a postable node does not aggregate its own value and that of its children, but only displays its own value part.
This means that the value of a node appears as follows (if the hierarchy uses the exception aggregation NGA):
If the node is a leaf or a posted node, the value is simply the node's own value (and not the aggregate of its subnodes).
If the node is a simple hierarchy node, its value is the total of all its posted sibling nodes, which can either be leaves or posted nodes. Siblings of posted nodes are ignored. Only the value of the posted node is taken into account.
NHA works in a similar way: This aggregation type also ensures that nodes with a postable value part (but which only aggregate the values of their children) are displayed as NULL. This means they have no value if they are not postable nodes.
The rules are simple with regard to the special values NULL, ERROR, or NOP. NGA and NHA do not specify any aggregation rules, they only define that the postable part of a postable node is included as the only value in the standard aggregation. Only the value of a postable node is included for the hierarchy exception aggregations NGA and HGA, irrespective of whether it is a special value or not. The rules of the standard aggregation SUM, MIN, and MAX are applied accordingly.