8 Designing Subject Areas

This chapter provides information about working with subject areas.

A subject area is a logical grouping of tables related to a particular subject or application context. A subject area includes the tasks that are associated with the tables, as well as the tasks required to load the tables.

Oracle BI Applications provides predefined subject areas. You can change these predefined subject areas or create new subject areas to correspond to your particular business processes.

Note:

To change a predefined subject area or to create a new subject area, you must first make a copy of an existing source system container or create a new container. For instructions, see "Creating or Copying a Source System Container".

This chapter contains the following topics:

• About Designing a Subject Area

• How DAC Determines Tasks Required for Subject Areas

• Creating a Subject Area

• Modifying an Existing Subject Area

• When to Reassemble a Subject Area

About Designing a Subject Area

In designing a subject area, you should consider the following questions:

• Tables. Which tables need to be populated in the data warehouse? From which tables does the organization source data? What tables will create the star schemas?

• Subject areas. Do the subject areas cover all the relevant tables?

• Tasks. Are the tasks that load this table defined?

• Indexes. Do the target tables have the correct indexes defined?

Previewing Subject Areas

You can preview a subject area to determine whether it contains the appropriate tables and tasks to suit your business needs. When you assign a fact table to a subject area, the fact table's related tables are automatically assigned to the subject area. If you determine you do not need one or more of the related tables, you can remove the tables during the subject area Assembly process. You can also add individual tables and tasks.

To preview a subject area, follow the procedure "Creating a Subject Area" through the assembly and review stages, but do not complete the process (by clicking Accept in the Subject Area Assembly dialog) unless the subject area is suitable for your needs.

How DAC Determines Tasks Required for Subject Areas

You define a subject area by specifying a fact table or set of fact tables to be the central table or tables in the subject area. When a subject area is defined, DAC performs the following process to determine the relevant tasks:

1. DAC identifies the dimension tables associated with the facts and adds these tables to the subject area.

2. DAC identifies the related tables, such as aggregates, associated with the fact or dimension tables and adds them to the subject area definition.

3. DAC identifies the tasks for which the dimension and fact tables listed in the two processes above are targets tables and adds these tasks into the subject area.

   Tasks that DAC automatically assigns to a subject area are indicated with the Autogenerated flag (in the Tasks subtab of the Subject Areas tab).

   You can inactivate a task from participating in a subject area by selecting the Inactive check box (in the Tasks subtab of the Subject Areas tab). When the Inactive check box is selected, the task remains inactive even if you reassemble the subject area.

   You can also remove a task from a subject area using the Add/Remove command in the Tasks subtab of the subject Areas tab, but when you remove a task it is only removed from the subject area until you reassemble the subject area.

4. DAC identifies the source tables for the tasks identified in the previous process and adds these tables to the subject area.

DAC performs this process recursively until all necessary tasks have been added to the subject area. A task is added to the subject area only once, even if it is associated with several tables in the subject area. DAC then expands or trims the total number of tasks based on the configuration rules, which are defined as configuration tags. This process can be resource intensive because DAC loads all of the objects in the source system container into memory before parsing.

Creating a Subject Area

When you create a new subject area, you assign one or more fact tables to the subject area. DAC then determines which dimension and other related tables are required as well as the tasks and their order of execution.

To create a new subject area

1. In the Design view, select the appropriate source system container from the drop-down list in the toolbar.

2. Click the Subject Areas tab.

3. In the top pane toolbar, click New.

4. In the Edit subtab, do the following:

   1. Enter a name for the subject area.

   2. If you want to assign only configuration tag tasks to the subject area and exclude the subject area's autogenerated tasks, select the Configuration Tag Tasks Only check box.

   3. Click Save.

5. Make sure the new subject area name is highlighted in the top pane, and click the Tables subtab.

6. Click Add/Remove in the subtab toolbar.

   The Choose Tables dialog is displayed. The left-hand window lists all the tables held in the selected container.

7. Query for one or more fact tables.

8. Select the fact table (use Shift+click to select more than one table), and click Add.

   The tables are added to the right-hand window, which represents the subject area.

9. Click OK to close the Choose Tables dialog.

10. In the top pane toolbar, click Assemble.

11. In the Assembling... dialog, select Selected Record Only.

    If you select the option All Records in the List, DAC will assemble all the subject areas listed in the top pane.

    DAC assembles the selected subject area by determining what dimensions and other related tables are required.

    The Subject Area Assembly dialog is displayed. The tree view on the left side shows the fact tables that belong to the subject area. You can expand the fact table node to view its related tables.

12. Click Calculate Task List to assemble the tasks needed to load the tables displayed in the tree view.

    If configuration tags have been assigned to any of the tasks, an information message will appear.

    A list of tasks is displayed in the Task List tab on the right side of the window. Also, the Table List tab displays the tables included in the subject area.

13. Click Accept to complete the subject area assembly process.

14. (Optional) Modify the subject area to better suit your business needs by removing one or more tables from the subject area.

    1. In the tree view, remove one or more tables from the subject area by deselecting the check box to the left of the table name.

    2. Click Calculate List.

    3. Review the changes to the subject area:

       The Task List tab displays the new set of tasks required to load the pruned subject area.

       The Task Difference Report tab displays the tasks that were added and the tasks that were deleted during the last assembly process.

       The Table List tab displays the tables that are included in the pruned subject area as well as the tables that were excluded during the pruning process.

    4. To accept the changes made to the subject area, click Accept.

    5. Click OK in the message box stating the subject area was successfully assembled.

15. (Optional) Click the Tasks subtab to view which tasks DAC has determined are required for this subject area.

    Tasks that are automatically assigned to the subject area by DAC are indicated with the Autogenerated check mark.

    You can inactivate a task from participating in the subject area by selecting the Inactive check box. When the Inactive check box is selected, the task remains inactive even if you reassemble the subject area.

    You can also remove a task from the subject area using the Add/Remove command, but when you remove a task it is only removed from the subject area until you reassemble the subject area.

Modifying an Existing Subject Area

You can modify an existing subject area by doing any of the of the following steps:

• Add or remove additional fact tables. You can add or remove fact tables using the Add/Remove command in the Tables subtab of the Subject Areas tab.

• Add or remove tasks. You can add or remove individual tasks using the Add/Remove command in the Tasks subtab of the Subject Areas tab. You can also remove tasks by assigning a task to a configuration tag. See "Working with Configuration Tags" for more information.

After you modify an existing subject area, you need to reassemble it (by selecting it and clicking Assemble in the Subject Areas tab). This action opens the Subject Area Assembly dialog, where you can calculate the new task list and view the tasks that were added and removed in the Task Difference Report tab.

When to Reassemble a Subject Area

After the first assembly of a subject area, you will need to reassemble the subject area in the following situations:

• A new task is added to the data warehouse that extracts data from or loads data into any of the tables associated with the subject area.

• A task associated with the subject area is deleted, activated or inactivated.

• A configuration tag is added to the subject area or to a table or task associated with the subject area.

Note: You do not need to reassemble a subject area if an attribute of a task changes but the task is already associated with a subject area.