Systems and methods for extending a directory schema independent of schema modification are described. In one aspect, a directory schema data structure includes a flexible attribute data field. The flexible attribute data field identifies a complex data type. The complex data type is used to express one or more operational or data providing properties of a flexible attribute. The one or more operational or data providing properties are independent of the complex data type and independent of directory schema modification. The directory schema data structure also includes a flexible structural object content class to encapsulate the flexible attribute.