Update Rules 
Definition
Update rules specify how data (key figures, time characteristics, characteristics) is updated into the InfoProvider from the communication structure of an InfoSource. You are therefore connecting an InfoSource with an InfoProvider.
As of SAP NetWeaver 2004s, the concept of update rules has been replaced by the new transformation concept. You can still create update rules, but we recommend that you use the new transformation concept. Transformations provide an easy-to-use, graphical maintenance interface. There is no longer a distinction between transfer and update rules; you only need to create transformation rules.
In the Data
Warehousing Workbench, the
symbol before
the description identifies an object that is available for the new
concept.
Use
An update rule must be specified for each key figure and the corresponding characteristics of the InfoCube. For a DataStore object, it must be specified for the data and key fields; for an InfoObject it must be specified for the attribute and key fields.
The following update types exist:
...
1. No Update
2. Addition, Minimum, or Maximum
3. Overwrite (DataStore objects and InfoObjects only)
A data target can be filled with data from several InfoSources. A set of update rules must be maintained for each of these InfoSources. These describe how the data is to be written into the data target from the communication structure for the InfoSource.
In the update, the InfoObjects of the communication structure for the InfoSource are referred to as source InfoObjects (source key figure or source characteristic). The InfoObjects for the InfoCube, on the other hand, are referred to as target InfoObjects (target key figure or target characteristic). Similarly, the InfoObjects of a DataStore object or InfoObject are referred to as target InfoObjects (target data field or target key field).
Structure
There is an update rule for each key figure of the InfoSource. This consists of the rule for the key figure itself and the rules for the characteristics, time characteristics, and units assigned to the key figure.