Common to these professional systems is that the three main areas that are the subject of investigation in a child protection case are illustrated by a triangular model. The triangular model is used as a starting point to categorize various cases related to the child's health and development, the parents' exercise of care and pressures on the family and environment. These main areas have their origins in an ecological understanding of children's needs and development. Central to this model is that the child's development is seen as the result of interaction between factors linked to the child himself and the child's developmental needs, the parents' care competence and conditions in the family and local environment.