Six Ways Large Systems Differ from Small Systems

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

(2) Large systems are 'brownfield systems' that include and interact with a number of existing systems — many requirements are concerned with this interaction

(3) Where several systems are integrated, a significant fraction of development is concerned with 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 it practically impossible to involve all of them in the development process

Explanation

Large systems differ from small in six ways: (1) collections of separate communicating systems developed by different teams; (2) brownfield systems interacting with existing systems; (3) significant system configuration work rather than original code; (4) constrained by external rules and regulations; (5) long procurement and development time making team coherence difficult; (6) diverse stakeholders making full involvement practically impossible.