The multi-tenant property of SaaS has brought new challenges to fine-grained access control. A common requirement in SaaS is logical data isolation for tenants. However, allowing data access across tenants is important in some scenarios. To achieve both goals, which are data isolation from tenants and data access across tenants, in this paper, the authors propose a data access configuration model for tenants. They then propose a flexible access policy specification method to describe what data are accessible by users.