Contemporary software systems, such as the Internet of Things (IoT), Industry 4.0, and Smart Cities are new technology paradigms that offer challenges for their construction since they are calling into question our traditional form of developing software. They are a promising paradigm for the integration of devices and communications technologies. It is leading to a shift from the classical monolithic view of development where stakeholder receive a software product at the end (that we have been doing for decades), to software systems materialized through physical objects interconnected by networks and with embedded software to support daily activities. We need therefore to revisit our way of developing software systems and start to consider the particularities required by these new sorts of applications. This paper presents research toward the definition of a framework to support the systems engineering of IoT applications, where we evolved the Zachman's Framework as an alternative to the organization of this architecture. The activities were two folded to address this goal: a) we identified leading concerns of IoT applications, recovered from technical literature, practitioners and a Government Report, in different studies; b) we structured the IoT paradigm in different facets. These activities provided 14 significant concerns and seven facets that together represent the engineering challenges to be faced both by research and practice towards the advancement of IoT in practice.