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An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types).
The enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or conceptual data model incorporating extensions to the original entity–relationship (ER) model, used in the design of databases.
A data structure diagram is a diagram type that is used to depict the structure of data elements in the data dictionary. The data structure diagram is a graphical alternative to the composition specifications within such data dictionary entries. [1] The data structure diagrams is a predecessor of the entity–relationship model (E–R model
Barker's notation refers to the ERD notation developed by Richard Barker, Ian Palmer, Harry Ellis et al. whilst working at the British consulting firm CACI around 1981. The notation was adopted by Barker when he joined Oracle and is effectively defined in his book Entity Relationship Modelling as part of the CASE Method series of books.
Euler diagram illustrating that the set of "animals with four legs" is a subset of "animals", but the set of "minerals" is a disjoint set (it has no members in common) with "animals" Euler diagram showing the relationships between different Solar System objects
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Resources, events, agents (REA) is a model of how an accounting system can be re-engineered for the computer age.REA was originally proposed in 1982 by William E. McCarthy as a generalized accounting model, [1] and contained the concepts of resources, events and agents (McCarthy 1982).
The split semisimple groups over k with given Dynkin diagram are exactly the groups G/A, where G is the simply connected group and A is a k-subgroup scheme of the center of G. For example, the simply connected split simple groups over a field k corresponding to the "classical" Dynkin diagrams are as follows: A n: SL(n+1) over k;