  The data generated by the devices and existing infrastructure in the Internet
of Things (IoT) should be shared among applications. However, data sharing in
the IoT can only reach its full potential when multiple participants contribute
their data, for example when people are able to use their smartphone sensors
for this purpose. We believe that each step, from sensing the data to the
actionable knowledge, requires trust-enabled mechanisms to facilitate data
exchange, such as data perception trust, trustworthy data mining, and reasoning
with trust related policies. The absence of trust could affect the acceptance
of sharing data in smart cities. In this study, we focus on data usage
transparency and accountability and propose a trust model for data sharing in
smart cities, including system architecture for trust-based data sharing, data
semantic and abstraction models, and a mechanism to enhance transparency and
accountability for data usage. We apply semantic technology and defeasible
reasoning with trust data usage policies. We built a prototype based on an air
pollution monitoring use case and utilized it to evaluate the performance of
our solution.
