The C4 level 1 system context around one system in scope A C4 context diagram fixes the boundary of one software system, names the people who use it above and the systems it relies on below, and labels every relationship, so everyone agrees what is inside the scope and what is outside before any deeper diagram.
The C4 level 1 system context around one system in scope
A C4 model system context diagram for a distribution network operator, laid out as a hub and spoke. At the centre, inside a dashed accent boundary, is the LTDS publication system, the one system in scope, which publishes network capacity data. Above it sit two people: a connections customer who reads data from it to check where capacity exists, and an Ofgem analyst who reviews it for compliance. Below it sit two external systems it depends on: a GIS it reads network geography from, and an asset register it reads ratings from. Accent arrows carry the verb on every relationship, and a legend separates the single system inside the boundary from the people and systems outside it.
People who use the system
Connections customer Checks where capacity exists Ofgem analyst Reviews compliance and data GIS Network geography and routes Asset register Ratings and asset records Reads data from Reviews Reads geography from Reads ratings from LTDS publication system Publishes network capacity data The one system in scope Systems the system depends on
Inside the boundary Outside, but connected Source: Simon Brown, c4model.com
