Data access layer: Difference between revisions

Revision as of 01:29, 3 January 2015

Revision as of 17:15, 21 July 2015

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A '''data access layer''' ('''DAL''') in computer software, 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 [[acronym]] is prevalently used in [[Microsoft]] [[ASP.NET]] environments.

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 (database)|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.

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[[Object-Relational Mapping]] tools provide data layers in this fashion, following the [[Active record pattern|active record]] model. The ORM/active-record model is popular with web frameworks.

== See also ==

* [[Data Access Object]]

* [[Database abstraction layer]]

== References ==

{{reflistReflist}}

== External links ==

* [http://msdn.microsoft.com/en-us/library/ee658127.aspx Microsoft Application Architecture Guide]

* [http://www.asp.net/web-forms/tutorials/data-access/introduction/creating-a-data-access-layer-cs ASP.NET DAL tutorial]

[[Category:Object-oriented programming]]