Currently, the Solid Protocol and its specifications lack the necessary vocabulary and processes for ensuring transparency and accountability in the use of data. In particular, to deal with the obligations and requirements required by regulations related to (personal) data protection and privacy. In addition, the lack of a guiding vocabulary leads to no common mechanism through which apps can request data and how Solid maintains information about its use. To address these, we propose PLASMA – a policy language to describe the entities, infrastructure, legal roles, policies, notices, and records to understand and establish responsibilities and accountability within the Solid ecosystem. We present how ontology design patterns using PLASMA can provide a common interface to create structured policies, records, and logs within the diverse Solid use cases, and thereby solve challenges regarding the management and governance of apps and their privacy considerations.