DAL and BLL ?

The main difference between the business logic layer and data access layer is that it returns a strongly-typed RecordCollection of Record objects, rather than a DataView. It also allows for Update, Insert, and Delete operations that take this Record object as a parameter. The ObjectDataSource DataObjectTypeName property allows you to configure the ObjectDataSource to pass this type to methods instead of individual field values. In the business logic layer method implementations, you can include custom logic for validating business rules. For example, you could ensure that only Records in the "In Review" category can be updated or only Administrators can insert new records. You can also include validation logic to ensure the data types and values supplied as arguments are correct before inserting or modifying data in the database. Note that validation logic in business layer is not a substitute for input validation at the presentation layer, which helps guide the end user to enter the correct values before submitting the update.

source:http://quickstarts.asp.net/QuickStartv20/aspnet/doc/ctrlref/data/objectdatasource.aspx