ABSTRACT
It is increasingly clear how the shift in planning from strong to weak rationality in the 1960s and 1970s (Simon 1957; 1977) and to dialogic interaction in the 1980s and 1990s (Forester 1999) has innovated and in some sense demystified the meaning and role of evaluation. In rational planning evaluation is essential for choosing one action from among alternatives that are available for achieving a goal (ex-ante evaluation) or for controlling an ongoing action during the process of achievement of a goal (ongoing evaluation), or for understanding how much a goal has been achieved at the end of the related action (ex-post evaluation). In communicative, discursive planning evaluation is like any other component of a planning procedure that has become discourse: the discursive form of argumentation (Forester 1989; Healey 1997; Khakee et al. 1995; Sager 1994), a form whose rationality features remain highly controversial (Provis 2004).As rational planning and communicative planning coexist (Friedmann 1987) also the two above cited forms of evaluation coexist, without clear prevalence of one over the other.
