-44 4.MONITORING VIOLENCE IN PRISON As explained above, violence is a complex and widespread phenomenon and therefore difficult to monitor effectively. The following section aims to offer practical guidance to NPMs on monitoring methodologies. 4.1. Setting the basis for the effective monitoring of prison violence 4.1.1. Gaining a good understanding of prison violence From the outset, it is important for NPMs to have a good understanding of prison violence and all factors contributing to it in general, but also in specific country contexts. This understanding should go beyond the number of violent incidents and other visible aspects contributing to violence and focus also on non-material aspects that are often hidden but equally relevant for preventing violence and ultimately ill-treatment. The research conducted in the framework of this Project, however, showed that NPMs tend to monitor only the measurable dimensions, such as incidents of direct violence and material detention conditions, and rarely address the factors indirectly causing and facilitating prison violence, such as structural violence, the prison culture as well as dynamic security and the elements underpinning it, including staff-prisoner relationships. To effectively monitor violence, however, it is essential to take into consideration all relevant aspects, also those that are less visible. The iceberg model illustrated in Figure 3 can be a useful tool for NPMs to visualise and map all the different dimensions relevant to understanding the problem of prison violence and its root causes. The model shows that only a limited fraction of the factors contributing to prison violence are visible, while