Two Archetypes of Entities in ERD

Some tables should just go down to the basic information of an object without any interaction needed, these are entities. but there are other entities are the consequences of interactions between objects and new attributes occur so we need to include these as entity as well.

🧩 Two Archetypes of Entities in ERD

1. Foundational Entities

These are the basic objects of the system—things that exist independently, without requiring interaction.

• Characteristics:

  • Have intrinsic identity and attributes.

  • Do not depend on other entities to exist.

  • Often represent physical or conceptual nouns.

• Examples:

  • Person (name, email, affiliation)

  • Manuscript (title, receive date)

  • Interest (IS code, description)

• Metaphor: These are the vaults—self-contained containers of truth.

2. Interaction-Derived Entities

These are entities that emerge from interactions between foundational entities and carry new attributes that cannot be derived from the participants alone.

• Characteristics:

  • Represent events, transactions, or relationships with their own data.

  • Require multiple entities to exist.

  • Cannot be reduced to a simple join or query.

• Examples:

  • Assignment (editor assigns manuscript to reviewers)

  • Authorship (person credited as author in a specific order)

  • ReviewFeedback (reviewer evaluates manuscript with ratings and recommendation)

• Metaphor: These are the ritual ledgers—records of interaction, with their own meaning and constraints.

As to what interactions can occur, it purely based on the reality and what needs to be done , or demands. This is also one linking point back business logics to back end system.

🔗 How Interactions Link ERD to Backend Logic

1. Reality → Interaction → Entity

• If something must happen in the real world (e.g., assigning reviewers),

  
  

  → it becomes an interaction.

  
  

  → if it has attributes and persistence, it becomes an entity (Assignment).

  
  

2. Interaction → Business Logic

• The backend must enforce the rules of that interaction:

• Who can assign?

• How many reviewers?

• Are interests matched?

• Is the author excluded?

These rules become:

• Event handlers (e.g., OnAssignmentCreated)

• Validation logic

• Triggers and workflows

  
  

3. Business Logic ↔ ERD

• The ERD defines what must exist.

• The backend defines how it comes into existence.

• Together, they form a contract between data and behavior.