Step 4: Define Output Interface
How Does Your System Deliver Its Output?
You've identified what your system produces and where it goes. Now you need to understand HOW it gets there - through what mechanism, process, or channel does your output actually leave your system?
This delivery mechanism is called an interface - the specific way your system connects with its environment to transfer outputs.
Creating the Interface
When you created your output flow in Step 3, you may have noticed it ends with a small rectangle at the system boundary. This rectangle becomes your interface.
Click on this rectangle to define your output interface:
Defining Your Interface
Click on the interface element to specify how your system delivers its output:
Name - What do you call this delivery mechanism? Examples from our model library:
Cell: "Cell Membrane Transport Proteins"
Ecosystem: "Predation Interface"
Solar Panel: "Electrical Output Terminals"
Organization: "Sales Interface" or "Service Delivery"
LLM: "Response Generation API"
Description - How does this interface actually work? What makes it effective at delivering your system's output to its environment?
Protocol - What rules or algorithm does this interface use to decide what goes out (and potentially what comes in)? This is the decision-making logic that governs the interface's behavior.
Understanding Interface Protocols
Think of a protocol as the "brain" of your interface - the set of rules that determine:
When to allow output to flow
What quality or quantity standards to maintain
How to handle different types of requests from the environment
What feedback to send back to the system
Examples:
Sales Counter: "Process orders during business hours, verify payment before releasing products"
Cell Membrane: "Allow glucose in when internal levels are low, expel waste when concentration exceeds threshold"
Website API: "Authenticate users, rate-limit requests, return error codes for invalid queries"
Interfaces are where your system meets the world. They're not abstract - they're the actual mechanisms, channels, or processes that make your outputs available to those who need them.
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