A computer-readable medium having stored thereon a data structure for an electronic data element. The electronic data element includes: a first data field containing data representing an identifier functioning as a link to one or more data objects; and a second data field representing a state of the identifier in the first data field. The second data field may be in one of three states: a) a first state, in which the electronic data element may be accessed by one or more data object processing operations and whereby said identifier is assignable to one or more data objects; b) a second state, in which said electronic data element may not be accessed by one or more data object processing operations and whereby said identifier is assignable to one or more data objects; or c) a third state, in which said electronic data element may not be accessed by one or more data object processing operations and whereby said identifier is not assignable to one or more data objects.