This work answers the following question, how to gather and act on personal data in smart city projects using boundary objects? Smart city projects require new mapping methods so they can share and discuss work collectively. Working collectively is necessary because smart city projects are difficult to map in one singular view for personal data because different smart city stakeholders have a part of the required information. Summarising data processing operations is most often taken for granted and under-defined in Data Protection Impact Assessment methods.This paper is a plea for the use of boundary objects for GDPR compliance and research in smart cities. Therefore, this article is a comparison of the original context boundary objects with the context of smart cities to illustrate the need for a similar approach. The main results of this paper point to a new approach to enable collaborative GDPR compliance where specialist knowledge trickles down to developers and other actors not educated to comply with GDPR requirements.