Conditional Relationship in Graph DB

Question

How would a graph model handle a conditional relationship like:

(Alice -[Dates]-> Bob)  
Where [Dates] exists IF and ONLY IF 
(Bob -[Owns]-> Ferrari) is true

Besides just querying, I'm wondering whether the relationship be applied by the database engine based on the condition or whether this needs to be managed in the application.

Answer 1

The answer of FrobberOfBits is very good and holds true for the ArangoDB database as well. However ArangoDB offers a micro-service framework called "Foxx" that allows you to define additional API endpoints for your database that can execute custom code.

One application for Foxx would exactly be your problem: * Define an endpoint to remove the relation that does two things: 1) Delete the relation 2) Check for all logical constraints or side-effects and apply them

This gives you the advantage that is executed directly in the database (only one query-trigger) and your application code is free of these constraints.