This paper presents the design phase of a work aiming at designing and developing a smart living device for seniors to assist them in their daily outdoor activities. We follow a participative design approach based on scenarios in order to design a socially-adapted device that will be useful to improve seniors’ life. To specify our system, we first provide an UML scenario metamodel to abstract all the concepts involved in our system collaborative functioning (interactions with stakeholders, environment …). This metamodel is used to generate different scenarios in order to better define future users ‘needs and the system requirements and notably its behavior (represented with BPMN and Petri Nets). A scenario generator has been implemented for that purpose. Finally, we show how to simulate and analyze those generated scenarios using process mining techniques.