In the Minimalist Program, Attract is a movement operation that is defined as follows: A target K attracts a feature F if F is the closest feature that can enter into a checking relation with a sublabel of K (Chomsky 1995:297).
Attract incorporates in its definition the global economy conditions Last Resort, Greed, and the Minimal Link Condition. The MLC is always respected because a functional head which has a feature that needs to be checked, always attracts the closest element. Last Resort does not have to be stated separately, because Attract only applies if there is a feature that needs to be checked. Greed is incorporated in Attract in so far that the functional head that attracts, can only attract in order to check a feature of its own. So it is not the moved element that is greedy, but the functional head (this is called Suicidal Greed). Incorporating these conditions into the definition of Attract has the advantage that at least for these principles, global evaluation is no longer necessary. This reduces computational complexity. In this system, the trigger for movement is always on the target. This has empirical advantages. In multiple questions in English, only one wh-element moves to C: (i) Who saw what? (i) shows that the trigger for wh-movement is not on the wh-elements themselves; if it were, what should also move to C.
Attract in Utrecht Lexicon of Linguistics
Chomsky, Noam A. 1995. The Minimalist program. Cambridge, MA: MIT Press. Category:Syntax