Abstract: We describe a model for multilevel information security. Information security is defined as combinations of confidentiality, integrity and availability. These three aspects are regarded as properties of a generic information object, and are treated as mutually independent. Each aspect is represented by an axis in an n-dimensional vector space, where n is the number of independent security aspects of interest. The model can ensure directed information flow along an arbitrary number of axes simultaneously. An information object is assigned a security label denoting the security level along an arbitrary number of axes. The model is role based. A role is assigned an access label along the same axes. Verification of a role's access to information is performed by comparing access label with security label. Since the aspects represented by each axis are mutually independent, each axis may be treated by itself. This enables a very efficient algorithm for verification of access.