  Agile methods have transformed the way software is developed, emphasizing
active end-user involvement, tolerance to change, and evolutionary delivery of
products. The first special issue on agile development described the methods as
focusing on "feedback and change". These methods have led to major changes in
how software is developed. Scrum is now the most common framework for
development in most countries, and other methods like extreme programming (XP)
and elements of lean software development and Kanban are widely used. What
started as a bottom-up movement amongst software practitioners and consultants
has been taken up by major international consulting companies who prescribe
agile development, particularly for contexts where learning and innovation are
key. Agile development methods have attracted interest primarily in software
engineering, but also in a number of other disciplines including information
systems and project management.
  The agile software development methods were originally targeted towards
small, co-located development teams, but are increasingly applied in other
contexts. They were initially used to develop Web systems and internal IT
systems, but are now used in a range of domains, including mission-critical
systems. Methods that were designed for single teams of 5-9 developers have
been adapted for use in projects with tens of teams, hundreds of developers,
which can involve integration with hundreds of existing systems and affect
hundreds of thousands of users.
