Logical Data Model
Logical Data Models (LDMs) represent data table (Entity Type) relationships.
A Logical Data Model (LDM)
Logical Data Model Notations
Entity Type
Entity Type refers to a group of related data placed in an RDBMS (Relational Database Management Systems) table. An entity is an instance of an entity type represented as a single row in a data table.
Learn how to convert a rectangle into a table.
Learn how to edit text on this object.
Relationships and Multiplicity
Relationships illustrate how two entity types are related. Cardinality specifies how many instances of an entity relate to one instance of another entity.
Ordinality is also closely linked to cardinality. While cardinality specifies the occurences of a relationship, ordinality describes the relationship as either mandatory or optional. In other words, cardinality specifies the maximum number of relationships and ordinality specifies the absolute minimum number of relationships.
Learn how to express cardinality in SmartDraw.
Child-Parent Markers
Use (C) to indicate that all child entities are deleted if the parent entity is deleted. Use (R) to indicate that the parent may not be deleted if children exist.
