Editing Defensive design (section)

{{Short description|Design practice that plans for contigencies}}
{{About|design to prevent misuse|the design of public places to prevent crime and other undesired actions|Hostile architecture}}
{{Unsourced|date=January 2024}}
[[File:G type plug and socket.png|thumb|[[BS 1363]] plug and socket, an example of defensive design: the plug can only be inserted in the correct orientation]]
'''Defensive design''' is the practice of planning for [[Contingency plan|contingencies]] in the [[design]] stage of a project or undertaking. Essentially, it is the practice of anticipating all possible ways that an end-user could misuse a device, and designing the device so as to make such misuse impossible, or to minimize the negative consequences. For example, if it is important that a plug is inserted into a socket in a particular orientation, the socket and plug should be designed so that it is physically impossible to insert the plug incorrectly. Power sockets are often keyed in such a manner, to prevent the transposition of live and neutral. They are also recessed in the wall in a way that makes it impossible to touch connectors once they become live.

Defensive design in [[software engineering]] is called [[defensive programming]]. [[Murphy's law]] is a well-known statement of the need for defensive design, and also of its ultimate limitations.