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.