1. An access control system for mediating access to an electronic resource comprising: an object entity residing in a computer memory having the following attributes each associated with integrity of the object entity: an integrity level attribute, and a write control attribute; a subject entity residing in the computer memory having the following attributes each associated with integrity of the subject entity: a read attribute, and a write attribute; wherein the integrity of the object entity and the subject entity is enforced by employing an access mediation rules system that is embedded as computer executable instructions in the computer memory and that implements the following rules with respect to said object entity and said subject entity: a first rule whereby writing by said subject entity into said object entity is inhibited if the write attribute of said subject entity is lower than said write control attribute of said object entity; a second rule whereby reading by said subject entity of said object entity is inhibited if the read attribute of said subject entity is lower than said integrity level attribute of said object entity; and a third rule whereby the write attribute of said subject entity is demoted to the level of said integrity level attribute of said object entity when said subject entity reads from said object entity and the integrity level attribute of said object entity is lower than the read attribute of said subject entity.