  Self-sovereign Identity promises to give users control of their own data, and
has the potential to foster advancements in terms of personal data privacy.
Self-sovereign concepts can also be applied to other entities, such as datasets
and devices. Systems adopting this paradigm will be decentralised, with
messages passing between multiple actors, both human and representing other
entities, in order to issue and request credentials necessary to meet
individual and collective goals. Such systems are complex, and build upon
social and technical interactions and behaviours. Modelling self-sovereign
identity systems seeks to provide stakeholders and software architects with
tools to enable them to communicate effectively, and lead to effective and
well-regarded system designs and implementations. This paper draws upon
research from Actor-based Modelling to guide a way forward in modelling
self-sovereign systems, and reports early success in utilising the iStar 2.0
framework to provide a representation of a birth registration case study.
