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Chapter 53: Building Multidimensional Cubes in Analysis Services with MDX
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Other Considerations
Data integrity functionality in Analysis Services addresses inconsistencies that would oth-
erwise cause improper data presentation. Analysis Services views these inconsistencies in
two categories: Null Processing and Key Errors. Analysis Services also enables deep confi gu-
ration on handling errors during processing.Best Practice
A key strength of OLAP, in general, and the UDM, in particular, is consistent interpretation of data. Data
integrity settings and centralized calculations are examples of the many ways that UDM centralizes data
interpretation for downstream data consumers. Address these issues in the design of the warehouse
and UDM to deliver the most useful product. Think of it as building a “data object” complete with
information hiding and opportunities for reuse.Null Processing
How you treat nulls depends on the NullProcessing property of the object in question.
For measures, the property appears as part of the source defi nition. Options include chang-
ing Nulls to zeros, throwing an error, or keeping the value as Null.A good way to choose among these settings is to consider how an average value should be
calculated on the data for a given measure. If the best interpretation is averaging only the
non-null values, then Preserve (keep as Null) yields that behavior. For dimensions, the
NullProcessing property can take on an additional value called Unknown Member, where
Null is interpreted as the unknown member. You can defi ne null handling on each attri-
bute’s NameColumn as well as each dimension attribute’s KeyColumn.Unknown Member
Choosing an unknown member option, either as part of null processing or in response to an
error, requires the unknown member to be confi gured for the affected dimension. After the
unknown member is enabled for a dimension, the member is added to every attribute in the
dimension. The UnknownMember dimension property can take on three possible settings:■ None: The unknown member is not enabled for this dimension, and any attempt to
assign data to the unknown member results in an error. This is the default setting.
■ Visible:The unknown member is enabled and is visible to queries.■ (^) Hidden: The unknown member is enabled but not directly visible in queries but is
accessible through MDX.
The default name of the unknown member is simply Unknown, which you can change by
entering a value for the dimension’s UnknownMemberName property.
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