Six Ways Large Systems Differ

(1) Large systems are usually collections of separate communicating systems where separate teams develop each — it is practically impossible for each team to see the whole system

(2) Large systems are 'brownfield systems' that include and interact with existing systems — requirements concern this interaction and don't lend themselves to incremental development

(3) A significant fraction of large system development concerns system configuration rather than original code development

(4) Large systems have a long procurement and development time making it difficult to maintain coherent teams

(5) Large systems usually have a diverse set of stakeholders making full involvement practically impossible

Explanation

Five of the six ways large systems differ: collections of separate communicating systems; brownfield systems interacting with existing systems; significant system configuration work; long procurement/development time making team coherence hard; diverse stakeholders making full involvement practically impossible. Large systems actually have more stakeholders, not fewer.