Types of rowset in DBMS rowsets

Database application programs use a rowset, which maintains a cursor on a current row within that set. The rowset provides an abstract interface, two types are provided:

a table is an entire table in a database. Row ordering is either undefined, or by one of the tables indexes. Fast key-based retrieval using an index can be performed on a table. The table is encapsulated in the derived class RDbTable.
an SQL view is a rowset generated by an SQL query on a database, currently restricted to a single table. Cursor navigation is implemented by evaluating the view as necessary. Since evaluation may be expensive, a pre-evaluation window may be specified, allowing the rowset to be evaluated once and navigated quickly. The desired window is described by the TDbWindow class. Rowsets can also be evaluated in steps. The SQL view is encapsulated in the derived class RDbView.