Data Modeling with Time-Dependent Master Data
- by Gary Nolan, SAP BI Strategic Architect, Sapiex Associates LLC
- April 1, 2004
Depending on the setup of your system, new master data can overwrite your old data when it is loaded. However, you can view data from a certain point in time with time-dependent master data. The author debates the benefits and drawbacks of adding time dependency to your data model.
Time-dependent master data allows you to display master data snapshots for a specific time or in its present state. This feature is useful if multiple views of master data are part of the reporting requirements. For example, reports could show master data attributes reflected as they were for a past quarter end or year end. There is, however, a cost for this frozen master data that you should weigh against the reporting benefits. I will explain these potential issues associated with creating and adding time-dependent master data to your data model.
The need for time-dependent master data arises because of the nature of master data itself. Each loaded record either creates a new record or replaces the attributes of the old master data record. After a load, the former master data view is lost. Any reporting analysis of past data — sales, for example — reflects the sales using the current view of the attributes and hierarchies of master data, not the views at the time of the transaction. This can be frustrating if you need reporting analysis showing the master data as it existed in the past, especially if the master data is frequently realigned. If you analyze prior sales using current master data, you could come to incorrect assumptions. To see the master data as it was in the past or when the transaction occurred could therefore make for a more complete view of the data.
You can add time dependency to text, hierarchies, and individual attributes of master data InfoObjects. When analyzing reporting requirements, you first determine what, if anything, needs to be time-dependent. Sometimes you can achieve some of the reporting requirements for time dependency by adding master data attributes to the transactional data when loading it into the InfoCube or ODS. This preserves a snapshot view of the specific master data attributes and transactional data. However, it cannot always satisfy the reporting requirements because this simply gives a view of master data for the time of the transaction, not for on-demand specific periods of time.
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