Entity relationship diagramming uses a standard set of symbols to represent each of these defined data groups and then proceeds by establishing the relationships between them. The first of these symbols is the soft-box entity symbol.
An entity is something about which data will be stored within the system under consideration. In this example the data group invoice can be identified as a system entity.
The other main component on a data model is the relationship line. A Relationship is an association between two entities to which all of the occurrences of those entities must conform.
The relationship is represented by a line that joins the two entities, to which it refers. This line represents two reciprocal relationships:That of the first entity with respect to the second, and that of the second entity with respect to the first.
Entity relationship diagramming is all about identifying entities and their relationships and then drawing a diagram that accurately depicts the system. This applies equally to the design of a new system or the analysis of an existing one.
The end result of entity relationship diagramming should be a clear picture of how information is stored and related within a proposed, or existing, system.
An entity is something about which data will be stored within the system under consideration. In this example the data group invoice can be identified as a system entity.
The other main component on a data model is the relationship line. A Relationship is an association between two entities to which all of the occurrences of those entities must conform.
The relationship is represented by a line that joins the two entities, to which it refers. This line represents two reciprocal relationships:That of the first entity with respect to the second, and that of the second entity with respect to the first.
Entity relationship diagramming is all about identifying entities and their relationships and then drawing a diagram that accurately depicts the system. This applies equally to the design of a new system or the analysis of an existing one.
The end result of entity relationship diagramming should be a clear picture of how information is stored and related within a proposed, or existing, system.