In their now classic article, 'Dilemmas in a general theory of planning', Rittel and Webber (1973) draw an important distinction between what they call 'tame' problems and 'wicked' problems. While not necessarily simple, tame problems generally have a relatively straightforward solution that is amenable to expert, technical knowledge. For instance, landing a man on the moon was an extremely complex undertaking, but it was possible to clearly articulate the objective and achieve it through the application of extant scientific knowledge. In problems like this, there are clear cause and effect mechanisms that enhance the likelihood that they can be solved (Batie 2008). Wicked problems, by contrast, are intractable, poorly structured and have only temporary or uncertain solutions (Rittel and Webber 1973). For wicked problems, there are no unambiguous criteria by which to judge their resolution. In fact, it is often difficult to define these problems in the first place because they usually involve intertwined normative criteria and empirical conditions or situations.