A conceptual schema or conceptual data model is a high-level description of informational needs underlying the design of a
database
In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...
. It typically includes only the core concepts and the main relationships among them. This is a high-level model with insufficient detail to build a complete, functional database.
It describes the structure of the whole database for a group of users. The conceptual model is also known as the
data model that can be used to describe the conceptual schema when a database system is implemented. It hides the internal details of physical storage and targets the description of entities, datatypes, relationships and constraints.
Overview
A conceptual schema is a map of
concept
A concept is an abstract idea that serves as a foundation for more concrete principles, thoughts, and beliefs.
Concepts play an important role in all aspects of cognition. As such, concepts are studied within such disciplines as linguistics, ...
s and their
relationships used for
database
In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...
s. This describes the
semantics
Semantics is the study of linguistic Meaning (philosophy), meaning. It examines what meaning is, how words get their meaning, and how the meaning of a complex expression depends on its parts. Part of this process involves the distinction betwee ...
of an organization and represents a series of
assertions about its nature. Specifically, it describes the things of significance to an
organization
An organization or organisation (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-ise, -ize (-isation, -ization), see spelling differences) is an legal entity, entity—such as ...
(''entity classes''), about which it is inclined to collect information, and their characteristics (''attributes'') and the associations between pairs of those things of significance (''relationships'').
Because a conceptual schema represents the semantics of an organization, and not a
database design, it may exist on various levels of abstraction. The original
ANSI
The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...
four-schema architecture began with the set of ''external schemata'' that each represents one person's view of the world around him or her. These are consolidated into a single ''conceptual schema'' that is the superset of all of those external views. A data model can be as concrete as each person's perspective, but this tends to make it inflexible. If that person's world changes, the model must change. Conceptual data models take a more abstract perspective, identifying the fundamental things, of which the things an individual deals with are just examples.
The model does allow for what is called
inheritance
Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Offi ...
in
object oriented terms. The set of
instances of an entity class may be subdivided into entity classes in their own right. Thus, each instance of a ''sub-type'' entity class is also an instance of the entity class's ''super-type''. Each instance of the super-type entity class, then is also an instance of one of the sub-type entity classes.
Super-type/
sub-type relationships may be ''
exclusive'' or not. A methodology may require that each instance of a super-type may ''only'' be an instance of ''one'' sub-type. Similarly, a super-type/sub-type relationship may be ''exhaustive'' or not. It is exhaustive if the methodology requires that each instance of a super-type ''must be'' an instance of a sub-type. A sub-type named "Other" is often necessary.
Example relationships
* Each PERSON may be ''the vendor in'' one or more ORDERS.
* Each ORDER must be ''from'' one and only one PERSON.
* PERSON is ''a sub-type of'' PARTY. (Meaning that every instance of PERSON is also an instance of PARTY.)
* Each EMPLOYEE may have a ''supervisor'' who is also an EMPLOYEE.
Data structure diagram
A
data structure diagram (DSD) is a data model or diagram used to describe conceptual data models by providing graphical notations which document entities and their relationships, and the constraints that bind them.
See also
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References
Further reading
* Perez, Sandra K., & Anthony K. Sarris, eds. (1995) Technical Report for IRDS Conceptual Schema, Part 1: Conceptual Schema for IRDS, Part 2: Modeling Language Analysis, X3/TR-14:1995, American National Standards Institute, New York, NY.
*
Halpin T,
Morgan T (2008) Information Modeling and Relational Databases, 2nd edn., San Francisco, CA: Morgan Kaufmann.
External links
* A differen
point of view as described by the
agile community
{{DEFAULTSORT:Conceptual Schema
Data modeling
Conceptual modelling