This paper discusses the types of mechanisms that can be used to implement Discretionary Access Control (DAC). It also covers the access types that can be controlled by a DAC mechanism. and includes a brief discussion of related topics including protected subsystems; administering, auditing, and verifying DAC; and DAC implemented as an add-on to an operating system. Finally this paper discusses how the DAC information presented in this paper will be used by the Department of Defense Computer Security Center in the preparation of a DAC Guideline to aid system designers and developers in their selection of DAC mechanisms.