  Multi-Criteria Decision Analysis (MCDA) is an established methodology to
support decision making of multi-objective problems. For conducting a MCDA, in
most cases a set of objectives (SOO) is required which consists of a
hierarchical structure with objectives, criteria and indicators. The
development of a SOO may require high organizational effort. This article
introduces elementary interactions as a key paradigm for the development of a
SOO. Elementary interactions are self-contained information requests that can
be answered with little cognitive effort, which are made and processed with the
help of a web platform. Each elementary interaction contributes to the stepwise
development of a SOO. Based on the hypothesis that a SOO can be developed
exclusively with elementary interactions, a platform concept is described.
Essential components of the platform are a Model Aggregator, an Elementary
Interaction Stream Generator, a Participant Manager and a Discussion Forum. The
platform concept has been evaluated in a pilot study using a web-based
prototype. In summary, the proposed concept demonstrates the potential to
advance the development of sets of objectives for MCDA applications: (1) The
platform concept does not restrict the application domain, (2) it is intended
to work with little administration efforts, (3) it lowers the organizational
effort for developing a SOO. (3) it supports the further development of an
existing SOO in the event of significant changes in external conditions. (4)
The development process of the SOO can be recorded by the platform and thus
becomes retraceable. The reproducibility may have a positive effect on the
spread of MCDA applications. The traceability and the use of elementary
interactions make the platform appear to be a suitable medium for Citizen
Science-based approaches to the development of MCDA applications.
