World Model

Overview#

A world model is a conceptual map of a system - a simplified representation that captures the essential building blocks, their relationships, and the rules that govern them.

The Map Analogy#

Just as a map is not the territory it represents, a world model is not the system itself. Maps serve specific purposes:

Similarly, a CFSE world model focuses on security-relevant structure, omitting implementation details that don't affect security properties.

Logic Layer vs Implementation Layer#

CFSE operates at two abstraction levels:

Logic Layer#

The logic layer contains abstract security rules independent of implementation:

• Concepts (what entities exist)
• Invariants (what rules must hold)
• Flows (what sequences are legitimate)

Example: "Only the owner of a resource can delete it"

Implementation Layer#

The implementation layer contains concrete realizations:

• Code (functions, classes, modules)
• Configuration (ACLs, policies, settings)
• Infrastructure (services, databases, networks)

Example: if resource.owner_id != current_user.id: raise PermissionDenied

Why Separate?#

Building a World Model#

A world model is built through progressive refinement:

1. Identify Concepts    -> What are the "nouns"?
2. Map Interactions     -> How do concepts connect?
3. Document Flows       -> What are legitimate sequences?
4. Define Invariants    -> What rules must always hold?

World Model Quality#

A good world model is:

Relationship to Artifacts#