Cairn Documentation

Quick Start

Get from zero to a working system model in under five minutes.

Prerequisites

A modern browser (Chrome, Firefox, Safari, Edge) and a free account. The free tier includes a limited number of nodes and AI calls — enough to explore the platform and build a small model.

Step 1: Describe Your System

Open the app and you'll see a text area asking what you want to build. Type a plain-language description of your system. It can be rough:

"An autonomous delivery rover with LIDAR navigation, hub motors, and a lockable cargo compartment"

"A portable weather station with solar power, cellular connectivity, and temperature/humidity/pressure sensors"

Don't worry about structure or completeness — that's what the next steps will help you figure out.

Step 2: AI Interview

Click Continue with AI → to start a short architecture interview. The AI asks 3-5 questions designed to surface important constraints and decisions:

What's the operating environment?
What are the critical performance requirements?
What interfaces does it need with external systems?

Select from the options the AI suggests, or type your own answer in plain language. Each round refines the system description and increases confidence. You'll typically go through 2-3 rounds before the AI has enough context to propose a structure.

Step 3: Review the Initial Decomposition

When you click Build →, the AI generates:

A root system node with your system description
4-7 subsystems with initial property estimates
Key interfaces between subsystems
A narrative brief summarizing the system

This appears as a ChangeSet — a list of proposed additions to your model. Review each item. Accept what looks right, reject what doesn't, or edit before accepting. Nothing changes until you approve it.

Step 4: Explore with Lenses

Your model now has structure. Select any node in the system tree (left sidebar) and explore it through different lenses (top tabs):

Overview — Dashboard with health metrics and children
Requirements — Functional, performance, and safety requirements
Architecture — Visual graph of child nodes and interfaces
Behavior — State machines for operational modes
Causality — What prerequisite technologies does this need?
Completeness — What's missing from this part of the model?

Each lens shows the same model from a different perspective. The data doesn't change — only how you view it.

Step 5: Refine with ⌘K

Press ⌘K (or Ctrl+K on Windows) to open the command palette. Type natural language requests scoped to your selected node:

"Decompose the power subsystem into battery, charging, and power distribution"

"Add thermal requirements for outdoor operation"

"Generate a state machine for the navigation controller"

The AI produces a ChangeSet. Review it operation-by-operation before applying.

What's Next

You now have a working model. From here you can:

Dive deeper into any subsystem (select it, run ⌘K to decompose)
Generate visual renders of components (Visuals lens)
Run simulations to validate power or mass budgets (Simulation tool)
Export to PowerPoint or Word for stakeholder review