Step 8: Traverse The Boundary

Does Your System Make Sense?

You've now mapped your system's key flows - primary output, waste, and inputs - along with their interfaces and sources/sinks. Time to step back and validate: does this tell a coherent story about how your system works?

Review Your Flow Logic

Look at your complete model and ask these critical questions:

Input-Output Balance: Do your inputs provide what's needed to create your outputs?

Examples from our model library:

• Cell: Glucose + Oxygen → Energy + CO2 + Water ✓

• Ecosystem: Sunlight + Nutrients → Biomass + Dead matter ✓

• Solar Panel: Solar radiation → Electricity + Heat ✓

• Organization: Materials + Labor → Products + Overhead ✓

• LLM: Prompts + Training data → Generated text + Computational heat ✓

Interface Consistency: Do your interfaces make sense for the flows they handle?

• Are input interfaces designed to receive what your sources provide?

• Are output interfaces designed to deliver what your sinks need?

Waste Accounting: Does your waste make logical sense given your inputs and processes?

Validation Questions

Energy/Resource Conservation: Where does the energy/matter come from and go to?

Purpose Alignment: Do your inputs support creating your primary output?

Environmental Fit: Do your sources and sinks exist in the same environment as your system?

Missing Elements: Are there obvious inputs or outputs you haven't accounted for?

What to Look For

Red flags that suggest revision needed:

• Outputs that require inputs you haven't identified

• Interfaces that don't match their flows

• Sources/sinks that seem disconnected from your system's environment

• Imbalanced resource accounting (more output than input, or vice versa)

Good signs your model is coherent:

• Clear transformation story from inputs to outputs

• Interfaces that make sense for their context

• Balanced resource accounting

• All flows have logical sources and destinations

Preparing for Internal Analysis

Once your input-output story makes sense, you're ready to look inside your system and understand how it actually transforms inputs into outputs through internal processes and subsystems.

A valid system model tells a believable story about transformation - how inputs become outputs through the system's processes, with waste as a natural byproduct. If your story has gaps, revisit your flows before proceeding to internal analysis.