**4. Discussion**

In this paper, the discussion is focused on a critical interpretation of the presented method itself. The key requirements specified in Section 2.1 are therefore chosen as a basis and deal as structure for the following investigation of the BiSA method. The main question to be answered can therefore be raised as follows: To which extent are the self-imposed goals of the developers achieved?

The general requirements have been set as consistency, comparability, reproducibility and falsifiability. Consistency of assessment systems is especially relevant with regard to system models. While the aim of the developers was to achieve full consistency of all aspects through the utilization of one system model, this could not be applied to the social function, as the building physical properties that provide the core of this aspect are not included in the life cycle inventory model that deals as a basis for the other aspects. Nevertheless, 5 out of 6 aspects could be modelled in a consistent way. Both comparability and reproducibility are met with the restriction of a not completely open model, which is caused by the fact that the underlying background databases are not publicly available. While consistency, comparability and reproducibility can be investigated on case study level, the falsifiability of sustainability in general is a critical requirement, as it simultaneously deals as a paradigm and as a scientific concept [94,95]. While the falsifiability of sustainability science and its scientific nature was questioned by Neumayer and Ziegler as well as Ott complemented the discourse and identified sustainability as a hybrid science that is falsifiable in the wider sense of conjecture and refutation [96]. In this sense, the presented framework offers a conjecture of BiSA open to refutation.

The basic requirements to decision support systems are met, even though their application has to prove true in future application. The proposed assessment system is able to support semi-structured and unstructured decisions and is applicable by decision makers throughout all phases of the decision making process. The requirements to sustainability assessment systems are classified based on the framework depicted in Figure 9 based on the experiences of previous applications. Overall, the assessment was developed by means of a comprehensive sustainability assessment with regard to the meta-assessment scheme, resulting in a classification of full strategicness, comprehensiveness and

integratedness. A medium classification in terms of transparency, boundary-orientedness, scalability and stakeholders' involvement can be specified.

**Figure 9.** Classification of the BiSA based on the findings of the first applications (adapted from Sala et al. (2015), figure licensed under CC BY NC ND) [19].

The requirements of bio-inspired systems are mainly focusing on the practical application properties. Therefore, the meeting of the bio-inspired requirements can only be validated through ongoing application, including feedback of practitioners. Nevertheless, the general structure of the assessment system is designed to be applicable by developers effectively and it is planned to adapt the assessment structure based on the feedback of the practitioners. However, these specifications cannot be validated with the amount of studies available. The resilience has been investigated through performing sensitivity analyses and already gave a hint that the social burden assessment shows unintended changes and potentially low resilience with regard to modelling artifacts in the background database. As far as this can be identified by the assessing experts, the resulting distortions can be limited. In any case, this indicates further research demand in the field of social burden assessment based on the LCWE method.
