Guide
Decision tree usage
We encourage the reader to visit our webpage, look around, get insights and start a discussion. Before doing so, however, it is important to understand a bit more about the usage of the tree; both conceptually and technically.
First and foremost, it is crucial to understand that the main objective of the tree is to facilitate the process of exploring the potential of several PETs as solution to your business problem. It achieves this objective by presenting the user with multidisciplinary questions and topics that need to be discussed already in an early stage of the process. At the same time, the user can explore the impact of the answers to these questions; for example, how the answers lead to a suggested PET solution. The discussions and explorations will often benefit by involving all stakeholders (business, risk officers, privacy officers, compliancy, data scientists, IT architects, end users). Although the decision tree always concludes by suggesting a PET suggestion, the real value is in the questions that lead you there.
Second, related to the final remark above, there may be many solutions to any problem. Rather than running through the tree once and expecting a definite outcome, it is more likely that multiple paths are feasible. For example, there may be a problem where one possible solution is to use a PET e.g. MPC, whereas another path might lead you to a different solution e.g. to outsource processing operations to a trusted third party. Both solutions have their advantages in terms of data protection compliance, data processing efforts, governance, flexibility and so on. From that perspective, the questions in the decision tree highlight some of the possibilities and potential requirements of a solution. These questions can thus facilitate the user in formulating, exploring, and discussing the requirements of the use case. Such discussions may in turn lead to adjusted use case requirements, which then lead to alternative paths in the decision tree. It is quite likely that several of these iterations are made in the development of a use case and exploring the possible solutions; in particular, you might walk through the tree many times while gradually improving your understanding of the problem and the applicable PET technologies. The tool checklist also facilitates this process.
Third, it is important that all organizations that participate in a collaboration should traverse the tree from their own perspective (again, involving all stakeholders). Different organizations may have different roles in the solution, e.g. they may share different types of data (if any) and their role from a legal or compliancy perspective may yield other restrictions or responsibilities. Every organization should think about their role in various potential solutions and discuss the implications and preferences collaboratively to identify the solution that works best for the collaborators as a group. Additionally, this applies to single aspects in the tree as well. Every challenge can be viewed from a different perspective and which of these is most important differs per organization. The main perspectives for addressing a challenge in the tree are depicted in the following figure.From a technical perspective, it is important to know both the fit and limitations in terms of end goal, IT setup or data science. Legal and compliance should be consulted to prevent potential legislative and privacy restrictions in a later stage. Lastly, there might be specific policy or supervisory guidelines within an organization that may limit the possibilities to use a specific implementation, for instance a restriction on setting up any third parties for the solution.
Fourth, it should be recognized that many challenges are composed of multiple smaller challenges. One should traverse the tree as many times as applications you wish to develop. For example, in the context of Machine Learning, you may run through once for model training and once for model evaluation.
Finally, we repeat and emphasize that the tool is no (legal) advise. It is extremely challenging to capture the complexity and context-dependency of generic real-world challenges and the subtleties in the variety of PET solutions in a tool. Instead, aiming at a first step in applying PET solutions, the purpose of the tool is to facilitate both the internal and external interdisciplinary discussion for organizations that are interested in using PETs for the challenges they face.