Editing Abstraction (computer science) (section)

==Levels of abstraction==
{{Further|Abstraction layer}}

Computer science commonly presents ''levels'' (or, less commonly, ''layers'') of abstraction, wherein each level represents a different model of the same information and processes, but with varying amounts of detail. Each level uses a system of expression involving a unique set of objects and compositions that apply only to a particular domain.
<ref>[[Luciano Floridi]], [http://www.cs.ox.ac.uk/activities/ieg/research_reports/ieg_rr221104.pdf ''Levellism and the Method of Abstraction'']
IEG – Research Report 22.11.04</ref>
Each relatively abstract, "higher" level builds on a relatively concrete, "lower" level, which tends to provide an increasingly "granular" representation. For example, gates build on electronic circuits, binary on gates, machine language on binary, programming language on machine language, applications and operating systems on programming languages. Each level is embodied, but not determined, by the level beneath it, making it a language of description that is somewhat self-contained.

===Database systems===
{{Further|Database management system}}

Since many users of database systems lack in-depth familiarity with computer data-structures, database developers often hide complexity through the following levels:

[[Image:Data abstraction levels.png|thumb|Data abstraction levels of a database system]]

''Physical level'' – The lowest level of abstraction describes ''how'' a system actually stores data. The physical level describes complex low-level data structures in detail.

''Logical level'' – The next higher level of abstraction describes ''what'' data the database stores, and what relationships exist among those data. The logical level thus describes an entire database in terms of a small number of relatively simple structures. Although implementation of the simple structures at the logical level may involve complex physical level structures, the user of the logical level does not need to be aware of this complexity. This is referred to as [[physical data independence]]. [[Database administrator]]s, who must decide what information to keep in a database, use the logical level of abstraction.

''View level'' – The highest level of abstraction describes only part of the entire database. Even though the logical level uses simpler structures, complexity remains because of the variety of information stored in a large database. Many users of a database system do not need all this information; instead, they need to access only a part of the database. The view level of abstraction exists to simplify their interaction with the system. The system may provide many [[view (database)|view]]s for the same database.

===Layered architecture===
{{Further|Abstraction layer}}
The ability to provide a [[design]] of different levels of abstraction can

* simplify the design considerably
* enable different role players to effectively work at various levels of abstraction
* support the portability of [[software artifact]]s (model-based ideally)

[[Systems design]] and [[Business process modeling|business process design]] can both use this. Some [[Software modeling|design processes]] specifically generate designs that contain various levels of abstraction.

Layered architecture partitions the concerns of the application into stacked groups (layers).
It is a technique used in designing computer software, hardware, and communications in which system or network components are isolated in layers so that changes can be made in one layer without affecting the others.