M2 Logical Data Model

A metamodel for logical data modelling — defining the structure of data independent of any specific database technology. Based on standard practices from Len Silverston’s Data Model Resource Book and the DAMA DMBOK.

Element Types (2)

Data Elements Layer

Type	Shape	Colour	Description
Entity	rectangle	#B5D4FF (light blue)	A concept about which data is recorded. Renders with name and attributes compartments.
Attribute	rectangle (subordinate)	#D4E8FF	A named, typed property of an Entity. Owned element — renders inside the Entity’s attributes compartment.

Entity Compartments

Entity renders with two compartments:

1. Name — entity name in bold, with <<Entity>> stereotype
2. Attributes — owned Attribute elements displayed using the template {name} : {Data Type}{Is Primary Key? [PK]:}

Attribute Properties

Property	Type	Required	Description
Data Type	Enumeration	Yes	String, Integer, Real, Boolean, Date, DateTime, Text
Is Primary Key	Boolean	No	Marks the attribute as part of the entity’s primary key
Is Required	Boolean	No	NOT NULL equivalent

Relationship Types (1)

Relationship	Line Style	Markers	Description
Related	solid	none	Association between two Entities with cardinality

Related Properties

Property	Type	Description
Cardinality	Enumeration	1:1 (one-to-one), 1:N (one-to-many), M:N (many-to-many)

Multiplicities and role names are shown on diagram edges.

Enumerations (2)

• Data Type — String, Integer, Real, Boolean, Date, DateTime, Text
• Cardinality — 1:1, 1:N, M:N

Design Principles

This metamodel is designed for third normal form (3NF) data modelling:

• Each entity represents a single concept
• Attributes depend only on the entity’s primary key
• Relationships capture associations with cardinality