Editing Law of Demeter (section)

{{Short description|Design guideline for software development}}
The '''Law of Demeter''' ('''LoD''') or '''principle of least knowledge''' is a design guideline for developing [[software]], particularly [[Object-oriented programming|object-oriented programs]]. In its general form, the LoD is a specific case of [[loose coupling]]. The guideline was proposed by Ian Holland at [[Northeastern University]] towards the end of 1987,<ref>{{Cite journal |last1=Lieberherr |first1=K.J. |last2=Holland |first2=I.M. |date=September 1989 |title=Assuring good style for object-oriented programs |url=http://dx.doi.org/10.1109/52.35588|journal=IEEE Software |volume=6 |issue=5 |pages=38–48 |doi=10.1109/52.35588 |s2cid=12651917 |issn=0740-7459|url-access=subscription }}</ref> and the following three recommendations serve as a succinct summary:<ref>{{cite web |url=https://github.com/emerleite/demeter |title= README.markdown: Demeter |last = Macedo |first= Emerson |publisher=GitHub |access-date=2012-07-05
}}</ref>
# Each unit should have only limited knowledge about other units: only units "closely" related to the current unit.
# Each unit should only talk to its friends; don't talk to strangers.
# Only talk to your immediate friends.

The fundamental notion is that a given object should assume as little as possible about the structure or properties of anything else (including its subcomponents), in accordance with the principle of "[[information hiding]]". It may be viewed as a corollary to the [[principle of least privilege]], which dictates that a module possess only the information and resources necessary for its legitimate purpose.

It is so named for its origin in the [[Demeter Project]], an [[adaptive programming]] and [[aspect-oriented programming]] effort. The project was named in honor of [[Demeter]], "distribution-mother" and the Greek [[goddess]] of [[agriculture]], to signify a [[top-down and bottom-up design|bottom-up]] philosophy of programming which is also embodied in the law itself.<ref>{{Cite web |title=Law of Demeter: Principle of Least Knowledge |url=https://www.khoury.northeastern.edu/home/lieber/LoD.html |access-date=2024-11-07 |website=www.khoury.northeastern.edu}}</ref>{{Non-primary source needed|date=November 2024}}