Note: This source should be combined with other sources at this level (check box)
Description: Check this box when data sources at the same level of aggregation do not contain
overlapping information. In this situation, all sources must be combined to get a complete picture
of information at this level of aggregation.
Note 2: To use a source correctly, the Analytics Server has to know what each source contains in
terms of the business model. Therefore, you need to define aggregation content for each logical
table source of a fact table. The aggregation content rule defines at what level of granularity the
data is stored in this fact table.
Use the Content tab of the Logical Table Source dialog box to define any aggregate table content
definitions, fragmented table definitions for the source, and Where clauses (if you want to limit the
number of rows returned).
Reference: Siebel Business Analytics Server Administration Guide > Creating and Administering
the Business Model and Mapping Layer in a Repository > Creating and Administering Logical
Table Sources (Mappings) > Defining Content of Logical Table Sources

Identity Store: It is directory server to perform the authentication. It contains user name , password and groups membership information .When a user name and password combination is entered at log in, the authentication provider searches the identity store to verify the credentials provided.
See figure below.

Explanation/Reference:
A: OBIEE Federated Repository
Instead of moving data in to a single database, OBIEE - BI Administration can access multiple databases and create a single federated repository.
OBIEE BI Answer uses this federated repository and build the ad-hoc reports and dashboards.
D: Repository Metadata Consists of 3 Layers
* The Physical Layer (Schema)
* The Business Model and Mapping Layer
* The Presentation Layer
Note:

Explanation
A measure column is a column unlike the baseline column that has a default aggregation rule defined in the Aggregation tab of the Logical Column dialog in the repository.
Measure columns always calculate the aggregation with which they are defined.
Measures need to be defined in a logical fact. Any column with an aggregation rule is a measure.
http://gerardnico.com/wiki/_media/dat/obiee/bi_server/design/obiee_measure_column.jpg

Explanation/Reference:
Pull the table and column definition into the physical layer
Use the OBIEE "import metadata" wizard to pull the table and column definition into the physical layer. The wizard is used so that all of the column definitions do not need to be manually added into the physical layer.
Figure:

Note: The physical layer is the layer of the Logical Business Model where you define the physical data model of your data source. It contains information about the physical data sources.