[[Continuous integration]] is the practice of merging all developer working copies to a shared [[Trunk (software)|mainline]] several times a day.<ref name=CI0>{{cite book
|title=Continuous Integration: Improving Software Quality and Reducing Risk
|author1=Paul M. Duvall
|author2=Steve Matyas
|author3=[[Andrew Glover]]
|isbn=978-0-321-33638-5
|publisher=[[Addison-Wesley Professional]]
|date=2007
}}
</ref>
[[Grady Booch]] first named and proposed CI in [[Booch method|his 1991 method]],<ref>{{cite book |last= Booch |first= Grady |author-link= Grady Booch |year= 1991 |title=Object Oriented Design: With Applications |url= https://books.google.com/books?id=w5VQAAAAMAAJ&q=continuous+integration+inauthor:grady+inauthor:booch |publisher= [[Benjamin Cummings]] |page= 209 |isbn= 9780805300918 |access-date= August 18, 2014 }}</ref> although he did not advocate integrating several times a day. [[Extreme programming]] (XP) adopted the concept of CI and did advocate integrating more than once per day – perhaps as many as tens of times per day.
