UDA is Microsoft's strategy for providing a common data access method for all types of data, regardless of where the data is located. UDA is based on OLE DB, a system-level component architecture for data management. UDA also defines an application-level programming interface for data access, ADO. ADO can be used from any programming language or tool that supports COM.
UDA is implemented by MDAC. MDAC includes ADO, an OLE DB provider for ODBC, as well as several ODBC components. In the ADO programming model, data is manipulated using Recordset objects.
A key feature of the ADO model for three-tier distributed applications is the ability to create disconnected Recordset objects that can be transmitted between middle-tier business objects and presentation-layer applications using RDS. Disconnected recordsets and RDS can help create the illusion that a user is permanently connected to a data store and can improve the scalability of the application.
We will discuss programming using ADO in more detail in Chapter 8, when we discuss building data objects. We will also look at working with disconnected Recordset objects again in Chapters 9 and 11, when we discuss building business objects and presentation-layer applications.