Lesson 3: Where to draw the lines between components
32 min read·
Module 4 · Lesson 3 · About 50 minutes · Needs: Module 3 lesson 1 (peak RPS, Little's law) and the shared data. No key: the model is a scripted stand-in behind the port
The situation
Week 4. Lessons 1 and 2 chose the rungs for Ask and Cases. Gareth now asks about the inside: Northdesk's first version answers Ask in one function that parses the request, writes the prompt, calls the provider and checks permissions. Where do the lines go, and should any become services?
The running example: t-tallis-u002, a Tallis finance employee, asks "How many days of annual leave do I get?". Tallis's 2026 policy says 30; its superseded 2025 policy says 29; Brennan & Kloss says 28. Part one draws the lines by the numbers; part two builds them with no model call.