In Continuation with Earlier post – Creating Physical layer of Repositories.
The Business Model and Mapping layer of the Administration Tool defines the business, or logical model of the data and specifies the mappings between the business model and the Physical layer schemas. This layer is where the physical schemas are simplified to form the basis for the users’ view of the data. The Business Model and Mapping layer of the Administration Tool can contain one or more business model objects. A business model object contains the business model definitions and the mappings from logical to physical tables for the business model.
The main purpose of the business model is to capture how users think about their business using their own vocabulary. The business model simplifies the physical schema and maps the users’ business vocabulary to physical sources. Most of the vocabulary translates into logical columns in the business model. Collections of logical columns form logical tables. Each logical column (and hence each logical table) can have one or more physical objects as sources.
There are two main categories of logical tables: fact and dimension. Logical fact tables contain the measures by which an organization gauges its business operations and performance. Logical dimension tables contain the data used to qualify the facts.
To build the Business Model and Mapping layer of a repository, you perform the following steps:
- Creating a Business Model
- Examining Logical Joins
- Examining Logical Columns
- Examining Logical Table Sources
- Renaming Logical Objects Manually
- Renaming Logical Objects Using the Rename Wizard
- Deleting Unnecessary Logical Objects
- Creating Simple Measures
Right-click the white space in the Business Model and Mapping layer and select New Business Model to open the Business Model dialog box.
Enter Sample Sales in the Name field. Leave Disabled checked.
Click OK. The Sample Sales business model is added to the Business Model and Mapping layer.
In the Physical layer, select the following four alias tables:
Do not select D4 Address at this time.
Drag the four alias table from the Physical layer to the Sample Sales business model in the Business Model and Mapping layer. The tables are added to the Sample Sales business model. Notice that the three dimension tables have the same icon, whereas the F1 Revenue table has an icon with a # sign, indicating it is a fact table.
Examining Local Joins
Right-click the Sample Sales business model and select Business Model Diagram > Whole Diagram to open the Business Model Diagram.
If necessary, rearrange the objects so that the join relationships are visible.
Because you dragged all tables simultaneously from the Physical layer onto the business model, the logical keys and joins are created automatically in the business model. This is because the keys and join relationships were already created in the Physical layer. However, you typically do not drag all physical tables simultaneously, except in very simple models. Later in this tutorial, you learn how to manually build logical keys and joins in the Business Model and Mapping layer. The process is very similar to building joins in the Physical layer.
Double-click any one of the joins in the diagram to open the Logical Join dialog box. In this example the join between D1 Time and F1 Revenue is selected.
Notice that there is no join expression. Joins in the BMM layer are logical joins. Logical joins express the cardinality relationships between logical tables and are a requirement for a valid business model. Specifying the logical table joins is required so that Oracle BI Server has necessary metadata to translate logical requests against the business model into SQL queries against the physical data sources. Logical joins help Oracle BI Server understand the relationships between the various pieces of the business model. When a query is sent to Oracle BI Server, the server determines how to construct physical queries by examining how the logical model is structured. Examining logical joins is an integral part of this process. The Administration Tool considers a table to be a logical fact table if it is at the “many” end of all logical joins that connect it to other logical tables.
Click OK to close the Logical Join dialog box.
Click the X to close the Business Model Diagram.
Examining Logical Columns
Expand the D1 Time logical table. Notice that logical columns were created automatically for each table when you dragged the alias tables from the Physical layer to the BMM layer.
Examining Logical Table sources
Expand the Sources folder for the D1 Time logical table. Notice there is a logical table source, D1 Time. This logical table source maps to the D1 Time alias table in the Physical layer.
Double-click the D1 Time logical table source (not the logical table) to open the Logical Table Source dialog box.
On the General tab, rename the D1 Time logical table source to LTS1 Time. Notice that the logical table to physical table mapping is defined in the “Map to these tables” section.
On the Column Mapping tab, notice that logical column to physical column mappings are defined. If mappings are not visible, select Show mapped columns.
You learn more about the Content and Parent-Child Settings tabs later in this tutorial when you build logical dimension hierarchies. Click OK to close the Logical Table Source dialog box. If desired, explore logical table sources for the remaining logical tables.
Creating simple Measures
Double-click the Revenue logical column to open the Logical Column dialog box
Click the Aggregation tab.
Change the default aggregation rule to Sum.
Click OK to close the Logical Column dialog box. Notice that the icon has changed for the Revenue logical column indicating that an aggregation rule has been applied.
Repeat the steps to define the SUM aggregation rule for the Units logical column.
Measures are typically data that is additive, such as total dollars or total quantities. The F1 Revenue logical fact table contains the measures in your business model. You aggregated two logical columns by summing the column data.
Save the repository without checking global consistency.
Now You have successfully built a business model in the Business Model and Mapping layer of a repository and created business measures.