Business Semantic Layers in BusinessObjects XI 3.1
A Business Semantic Layer in a Business Intelligence platform is a data layer which consolidates data for immediate business consumption. it allows for a standardized set of data definitions and business terms across the enterprise. It also allows business users to directly tap into their data sources without dealing with the complexities of data and database management.
Although not truly semantic (yet), the business semantic layer provides an interface to Business users to create their own reporting and analytics. The business semantic layer is usually developed by the data and information management teams or IT and is usually coupled with data privacy and organizational security policies.
There are two business semantic layers provided by BusinessObjects, the Business Views (developed through the client tool Business Views Manager) and the Universe (developed through the client tool Designer). The former comes from the acquisition of Crystal Decisions and the latter is its own home grown layer. It has been touted on several occasions by BusinessObjects of launching a unified semantic layer, however, it hasn’t arrived just yet.
The two layers offer many redundant functionality, however, both serve specific purposes. If you are planning to use Web Intelligence only, then you are left with no choice but to use Universes. However, if you are using Crystal Reports, then you have a fair deal of decision making to do before you can finally pin down to either Business Views or Universes or maybe even both.
Here are some Pros and Cons of both approaches for your decision making:
Secure Distribution:
Universes allow row level security. This means that users can define row level filtering based on group and user policies. However, for scheduling reports on an enterprise group security matrix, a single report has to be scheduled each time the row level security changes for the groups (or users).
This isn’t a very efficient approach, and when scaling out, it creates a lot more instances than when using business views. Business Views uses view level security. This means user can define business views for each unique group (or user). The advantage is that the report instance remains just one for each unique group(user) having a distinct data security.
Aggregate Awareness:
Aggregate Awareness is the ability to understand dimensional hierarchies when rolling up aggregates. The capability to define dimensional hierarchies is only present in Universe. Business Views are more like flat structures and there is no real differentiation between objects in the structure. Unlike Universes, Business Views don’t have Measures, Details, Dimensions or Classes and they also don’t have support for hierarchical relationships. Therefore, aggregate functions are not optimized in terms of roll up.
This means that if there are three functions, sum(week), sum(month), sum(year), Universes re-use the aggregate values from lower grains and roll up to higher ones, whereas Business Views treat them all independent of their relationship to one another.
Business Contexts:
Like Aggregate Awareness, Business Views don’t support Query Contexts as well from Universes. This means that for multiple join paths between tables, Business Views don’t provide any information to optimize the query path to the SQL optimizer. This leads to lesser performance. However, business views seldom enter into loops due to the separation of layers for Business Elements.
Limitations of Using Universes with Crystal Reports:
Although Crystal Reports can read from both Business Views and Universes, there are known limitations of using universes as a data source for crystal.
Check out the limitations here
My recommendation to use Business Views or Universe comes from the basic usage of the two reporting products.
For operational reporting with limited metrics (in terms of aggregations etc) but more focus on information distribution, Business Views are preferred.
For more management and analytical reporting needs with relatively greater number of metrics and with lesser security groupings, Universes are better.
However, based on the above points, it all depends on the exact needs of the customer from the platform and the tools to really decide which way to go.
The future is a unified semantic layer from BusinessObjects…
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