Data access layer: Difference between revisions

Revision as of 03:44, 26 October 2009

Revision as of 20:33, 31 October 2009

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A '''Data Access Layer''' (DAL) is a [[layer (object-oriented design)|layer]] of a [[computer program]] which provides simplified [[access]] to [[data]] stored in [[persistent storage]] of some kind, such as an [[entity relationship|entity-relational]] [[database]].

This data access layer is used in turn by other program modules to access and manipulate the data within the data store without having to deal with the complexities inherent in this access.

For example, the DAL might return a reference to an [[object (computer science)|object]] (in terms of [[object-oriented programming]]) complete with its attributes instead of a [[row]] of [[Field (computer science)|fields]] from a database [[table (database)|table]]. This allows the client (or user) modules to be created with a higher level of [[abstraction]]. This kind of model could be implemented by creating a class of data access methods that directly reference a corresponding set of database stored procedures. Another implementation could potentially retrieve or write records to or from a file system. The DAL hides this complexity of the underlying data store from the external world.