Specifies whether to generate the list of elements that may substitute for the given element.
Typically, these are the members of the substitution group headed by the given element.
Note that the head of a substitution group may be a member of other substitution group (with a different head) and so on. Thereby, the subsitution groups may form an hierarchy.
So, the list of substituting elements may potentially include all members of the subsitution group hierarchy
attached to the given element. However, that is not always the case. Some of those members may be abstract or blocked from substitutions
by the setting of |
Applies To: