Agile is a stretch to fit approach, Cockburn (2002, specific reference to Crystal and other later references to Agile generically)

Traditional/RUP is a shrink to fit approach (Rational 2005 and other references)

Kanban is an evolve for fitness approach (Anderson 2011)

In this sense, Kanban is both a differentiated and 2nd generation approach to improving agility, and a direct approach to addressing the complex nature of the software development and IT services domains.

For more information on Kanban, please refer to David Anderson's book "Kanban" or visit http://limitedwipsociety.org