45 2 EXTENSIVE LITERATURE REVIEW impacts the lives of others besides the designers, as is often the case’. The top level of a value hierarchy consists of the values, as depicted in Figure 3, the middle level contains the norms, which can be capabilities, properties or attributes of the artefact, and the lower level are the design requirements that can be identified. The relation between the levels is not deductive and can be constructed top-down, by means of specification, or bottom-up by seeking for the motivation and justification of the lowerlevel requirements. The bottom-up conceptualisation of values is a philosophical activity which does not require specific domain knowledge and the top-down specification of values requires context or domain specific knowledge that adds content to the design (Van de Poel, 2013). Value Norm Norm Requirement Requirement Requirement Requirement Requirement Figure 3: Conceptual model value hierarchy Van de Poel (2013, p. 262) defines specification as: ‘as the translation of a general value into one or more specific design requirements ’ and states that this can be done in two steps: 1. Translating a general value into one or more general norms; 2. Translating these general norms into more specific design requirements. For step 1 two criteria are relevant: (1) the norm should be an appropriate response to the value and (2) the norm should be a sufficient response to the value. In step 2 the requirement should be more specific regarding the scope of applicability, goals and aims strived for, and actions to achieve those aims of the norm (Van de Poel, 2013). The value
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