Data access typically refers to software and activities related to storing, retrieving, or acting on data

Data

The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

 housed in a database

Database

A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

 or other repository. There are two types of data access, sequential access

Sequential access

In computer science, sequential access means that a group of elements is accessed in a predetermined, ordered sequence. Sequential access is sometimes the only way of accessing the data, for example if it is on a tape...

 and random access

Random access

In computer science, random access is the ability to access an element at an arbitrary position in a sequence in equal time, independent of sequence size. The position is arbitrary in the sense that it is unpredictable, thus the use of the term "random" in "random access"...

.

Historically, different methods

Method (computer science)

In object-oriented programming, a method is a subroutine associated with a class. Methods define the behavior to be exhibited by instances of the associated class at program run time...

 and languages were required for every repository, including each different database, file system

File system

A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

, etc., and many of these repositories stored their content in different and incompatible formats.

In more recent days, standardized languages, methods, and formats, have been created to serve as interfaces between the often proprietary, and always idiosyncratic, specific languages and methods. Such standards include SQL

SQL

SQL is a programming language designed for managing data in relational database management systems ....

, ODBC, JDBC, ADO.NET

ADO.NET

ADO.NET is a set of computer software components that programmers can use to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems,...

, XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

, XQuery

XQuery

- Features :XQuery provides the means to extract and manipulate data from XML documents or any data source that can be viewed as XML, such as relational databases or office documents....

, XPath

XPath

XPath is a language for selecting nodes from an XML document. In addition, XPath may be used to compute values from the content of an XML document...

, and Web Services.

Some of these standards enable translation of data from unstructured (such as HTML or free-text files) to structured (such as XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

 or SQL

SQL

SQL is a programming language designed for managing data in relational database management systems ....

).