Editing Logical schema (section)

== Logical data model topics ==

=== Reasons for building a logical data structure ===
* Helps common understanding of business data elements and requirement
* Provides foundation for designing a database
* Facilitates avoidance of [[data redundancy]] and thus prevent data and business transaction inconsistency
* Facilitates data re-use and sharing
* Decreases development and maintenance time and cost
* Confirms a logical [[process model]] and helps [[impact evaluation|impact analysis]].

=== Conceptual, logical and physical data model ===
A logical data model is sometimes incorrectly called a physical data model, which is not what the ANSI people had in mind. The physical design of a database involves deep use of particular database management technology.  For example, a table/column design could be implemented on a collection of computers, located in different parts of the world.  That is the domain of the physical model.

Conceptual, logical and physical data models are very different in their objectives, goals and content. Key differences noted below.

{| class="wikitable"
|-
! Conceptual data model (CDM)
! Logical data model (LDM)
! Physical data model (PDM)
|-
| Includes high-level data constructs
| Includes entities (tables), attributes (columns/fields) and relationships (keys)
| Includes tables, columns, keys, data types, validation rules, database triggers, stored procedures, domains, and access constraints
|-
| Non-technical names, so that executives and managers at all levels can understand the data basis of Architectural Description
| Uses business names for entities & attributes
| Uses more defined and less generic specific names for tables and columns, such as abbreviated column names, limited by the database management system (DBMS) and any company defined standards
|-
| Uses general high-level data constructs from which Architectural Descriptions are created in non-technical terms
| Is independent of technology (platform, DBMS)
| Includes primary keys and indices for fast data access.
|-
| Represented in the [[Department of Defense Architecture Framework|DIV-1]] Viewpoint (DoDAF V2.0)
| Represented in the DIV-2 Viewpoint (DoDAF V2.0), and OV-7 View (DoDAF V1.5)
| Represented in the DIV-3 Viewpoint (DoDAF V2.0), and SV-11 View (DoDAF V1.5)
|-
|}