Entities are logical groupings of information. Each entity is represented by a box containing text. The text is usually a noun or a combination of adjective(s) and a noun.
Pathways Note: The ERDs for the Pathways project are divided into broad areas of information. When an entity appears in more than one ERD, it will appear with shading in all but one diagram to indicate that it is defined elsewhere. The Subject Requirement entity in one of the following sample diagrams illustrates this.
Entities may interact with each other to form relationships. A relationship is represented by a diamond shape containing a verb that describes the relationship. The diamond is connected to each entity involved in the relationship by a line with one or two arrows pointing to the entity.
The arrows indicate the cardinality of the relationship. A single arrow indicates that the relationship exists for each individual entity; a double arrow indicates that one or more entities may be involved in the relationship. For example,. the diagram above indicates that the University has more than one minimum admission requirement.
An entity may represent a generalized grouping of information. Specializations of the entity are represented by additional boxes connected to the entity and arranged in a hierarchy. The generalized entity is the supertype, and is identified by a horizontal line crossing its connecting line. Specializations, the subtypes, do not have horizontal lines crossing the connecting line.
The diagram above indicates that there are three subtypes of the minimum eligibility requirement: the subject requirement, the scholarship requirement, and the examination requirement.
An associative entity is a grouping of information associated with a relationship -- i.e. information about the interaction between other entities. An associative entity is represented by a box containing a qualified noun, just like other entities. However, unlike other entitities, it is connected to a relationship symbol by a dashed line and an arrow pointing toward the relationship symbol.
The diagram above indicates that a high school course may satisfy one or more subject requirements and that information about each requirement satisfaction (i.e. the relationship) is recorded in the high school course certification associative entity.