These relationships can be difficult to identify and to resolve. Here there are many charters and many witnesses. Each charter can have more than one witness each witness can sign more than one charter. The table chartsign will just contain references to the witness and charter tables. They become important later in that the values of attributes are the data that is to be recorded in the database.
Attributes represent the data that is to be kept about the entities.
They cannot exist independently of the entities. There are certain things known about the charters and the witnesses that are relevant to the political and social influence of a small group of people near to the king. There was a further complexity not shown in this model. So a full model would need two further entities, of office and status. A witness can have many offices over time and can change status over time.