Glossary¶

A collection of key terms used in ThinkERD and data modeling.

ERD Fundamentals¶

Entity: A unit of data collection to be managed by the business. In the logical model it's an entity; in the physical model it corresponds to a Table. Examples: Customer, Order, Product
Attribute: An individual data item that makes up an entity. In the physical model, it corresponds to a Column. Examples: Customer Name, Email, Registration Date
Relationship: The business association between two entities. Defining a relationship creates an FK column and displays a relationship line on the canvas.
PK (Primary Key): An attribute (or combination of attributes) that uniquely identifies each row within an entity. In Barker's Notation, shown with a # marker and UID Bar.
FK (Foreign Key): An attribute that references another entity's PK. Automatically generated through relationships.
Cardinality: Indicates how many rows in one entity can be associated with a single row in the related entity. Types include 1:1, 1:N, and M:N.
Optionality: Indicates whether participation in a relationship is Mandatory or Optional. In Barker's Notation, expressed as solid line (mandatory) / dashed line (optional).

Barker's Notation: An ERD notation developed by Oracle's Richard Barker. Expresses identifying/non-identifying relationships, cardinality, and optionality at a glance through relationship line shapes (solid/dashed, forked ends). → Barker's Notation Guide
Identifying Relationship: A relationship where the FK forms part of the child entity's PK. Represented by a solid line in Barker's Notation. Means the child cannot exist without the parent.
Non-Identifying Relationship: A relationship where the FK is a regular attribute of the child entity. Represented by a dashed line in Barker's Notation. The child can exist independently.
UID Bar: A vertical bar on the left side of the entity that visually emphasizes PK columns. For composite PKs, the bar spans multiple columns.
Subtype: A sub-category of a supertype entity. In Barker's Notation, represented as nested boxes within the entity. Example: Employee → Permanent, Contract, Intern → Subtypes Guide
Exclusive Arc: A constraint where only one of multiple relationships can be active. Represented by an arc symbol. Example: Payment connected to either Credit Card or Bank Transfer → Exclusive Arcs Guide

Standard Word: The smallest mapping unit between logical and physical names. Example: Customer(CUST), Number(NO), Date(DT)
Standard Term: A business term composed from standard words. Example: Customer No(CUST_NO) = Customer(CUST) + Number(NO)
Standard Domain: A classification system that defines data type and length for an attribute. Example: Amount domain → Oracle: NUMBER(18,2), PostgreSQL: NUMERIC(18,2) → Words, Terms & Domains

Solo Mode: REST API-based synchronization mode used when a single user is editing. Efficient and lightweight.
Live Mode: WebSocket-based real-time synchronization mode that auto-activates when multiple users are editing simultaneously. → Solo vs Live Mode
Awareness: A feature in Live Mode that shares other users' cursor positions, selections, and online status in real time.
Tab Leader: The leader tab that coordinates synchronization in Live Mode. Auto-elected among tabs — users don't need to be aware of it.

SQL Scratchpad: An editor for executing SQL queries within the browser based on ERD entity structures. No external DB connection needed.
Mock Data: Auto-generated sample data for query testing in the SQL Scratchpad.
SPARQL: A graph query language for semantic querying after converting ERD structures to RDFS/OWL ontology. → SPARQL & Ontology
Ontology: A model that semantically defines concepts and relationships of a data structure. ERD entities are mapped to owl:Class, and relationships to owl:ObjectProperty.