This is not a technical architecture diagram. It's not code. It's the functional blueprint that describes what the system does, block by block, before anyone writes a line of code.

Examples

What it contains

The Logical Functional Architecture maps the system as a sequence of functional blocks. For each block, you define:

Element	What it specifies
Block name	What this step does, in plain language
Block type	Gen AI, deterministic, retrieval, algorithmic, human
Input	What this block receives — from the user or from the previous block
Output	What this block produces — for the next block or for the end user
Logic	What happens inside — the prompt, the rule, the query, the human action
Validation	How you know this block performed correctly
Failure mode	What goes wrong here, and what happens when it does

The five types of blocks

Every functional block in the architecture falls into one of five types:

1. Gen AI block

The system interprets, extracts, generates, or reasons using a language model.

Defined by:

The prompt — what instructions does the model receive?
The input context — what data is passed in?
The expected output structure — what should come back?