There is a huge disparity in how these terms are used, sometimes DS, DA and BA are used interchangeably. Although, the gap is narrowing now, BA is strictly dealing with advanced analytics but DS is more about bringing predictive power using machine learning techniques. One thing is clear, Data Modelling typically means designing the scheman etc. Though there are no hard rules that distinguish one from another, you should get the role descriptions clarified before you join an organization.