UDM Appendix A - UML Notation & Conventions

This section explains the principles, patterns, and conventions used for the Ed-Fi Unifying Data Model.

Ed-Fi Unifying Data Model

The Ed-Fi Unifying Data Model (UDM) is a conceptual model, and a common framework for the representation of data in the education domain. The UDM serves as the enterprise data model which is the basis for all Ed-Fi Data Exchange Standards.

Notation

The Ed-Fi UDM is expressed as Unified Modeling Language (UML) Class diagrams to capture the logical structure of a domain as a set of classes, their features (attributes), and the relationships (associations) between them. UML Class diagrams are more useful than Entity-Relationship diagrams to understand the Ed-Fi Unifying Data Model because they support generalization of classes.

UML Diagram Conventions

In the Ed-Fi UDM, classes represent the major entities or objects in the education domain, such as students, teachers, campuses, and locations. Additionally, classes model non-physical entities in the education space, such as courses, sections, attendance events, and discipline actions.

The class attributes represent properties or characteristics of entities that are important in the education domain. Complex attributes with many components are defined as separate classes and referenced as the type of the attribute. For example, the complex attribute type Address has the components street address, city, state, and ZIP code. Unless otherwise indicated, attributes are of cardinality 1, meaning that they are single-valued and required. Other cardinalities are shown within square brackets.

Relationships or associations represent logical connections between entities that are important in our education domain.

For example, students are associated with campuses through enrollment. The direction of an association indicates readability (as in Student HasAssociated School) in the domain model. The direction of the association has additional meaning in the XML Schema, indicating the class from which the relationship is specified. Cardinalities (e.g., 1-to-1, 1-to-many, many-to-many) are shown for all associations.

An association class is used when an association has attributes. For example, the date of enrollment is an important attribute of the Enrollment Association between student and campus.

A generalization association indicates that a more specialized subclass is a generalization of a broader superclass. For example, a campus or school is a specialization of the more general Education Organization. The attributes and associations defined for the superclass are inherited by the more specialized subclasses. Generalization semantics are compatible with Type extensions in XML schemas.

Notes are included in the Ed-Fi Unifying Data Model to explain or elaborate on points not obvious from the UML model structure or class names.

Association Labels

The Ed-Fi UDM uses the following association labels. These were originally adapted from the National Education Data Model (NEDM) project.

Table 1: Association Labels and Definitions in the Ed-Fi Data Model

UDM Naming Conventions

The Ed-Fi Data Standard naming conventions are detailed below. Consistent naming is used across all Ed-Fi technical artifacts.

General naming conventions are as follows:

• Concatenated title case is used for entities, relationships, and attributes (e.g., “SchoolId”)
• Names use common terminology for the education industry

Generally, the entity and attribute names align with those of CEDS with the following exceptions:

• If there is not an analogous name in CEDS
• If the CEDS name does not reflect common terminology or is unnecessarily long
• When the CEDS name conflicts with Ed-Fi naming conventions and guidelines

By default, association names are formed as follows:

• Associations with attributes are named by concatenating the two entities they relate and ending with “Association”, e.g.,  “StudentSchoolAssociation”
• When there can be two associations between the same pair of entities, a semantic discriminator is added, e.g.,  StaffEducationOrganizationEmploymentAssociation, StaffEducationOrganizationAssignmentAssociation

Extensions to the Ed-Fi Data Standard should carry forward the naming conventions. The same naming conventions apply to the Ed-Fi UDM, the Ed-Fi REST API Specifications, and the associated Ed-Fi XML schemas. For additional and specific rules for how the naming conventions apply to the REST APIs, see API Design & Implementation Guidelines. For the Ed-Fi XML-based data standards, see XSD Design & Implementation Guidelines.