 
            | ClassGroup | A reference to a class group. Only available when StructureType = MFMetadataStructureItemClassGroup Will not be serialized if unavailable. | 
| ID | A reference to a value of an unknow structure type. Only available when StructureType = MFMetadataStructureItemNone Will not be serialized if unavailable. | 
| NamedACL | A reference to a named ACL. Only available when StructureType = MFMetadataStructureItemNamedACL Will not be serialized if unavailable. | 
| ObjectClass | A reference to a class. Only available when StructureType = MFMetadataStructureItemClass Will not be serialized if unavailable. | 
| ObjID | Alias of ValueListItem. Will never be serialized. | 
| ObjType | A reference to an object type. Only available when StructureType = MFMetadataStructureItemObjectType Will not be serialized if unavailable. | 
| PropertyDef | A reference to a property def. Only available when StructureType = MFMetadataStructureItemPropertyDef Will not be serialized if unavailable. | 
| Reference | The reference currently set in the object. Available regardless of StructureType. | 
| State | A reference to a state. Only available when StructureType = MFMetadataStructureItemState Will not be serialized if unavailable. | 
| StructureType | The type of structure item the current reference refers to. | 
| Transition | A reference to a state transition. Only available when StructureType = MFMetadataStructureItemStateTransition Will not be serialized if unavailable. | 
| Type | The MFilesAPI type that the StructureType corresponds to used for resolving id's with MFIdentifier. | 
| User | A reference to a user. Only available when StructureType = MFMetadataStructureItemUser Will not be serialized if unavailable. | 
| UserGroup | A reference to a user group. Only available when StructureType = MFMetadataStructureItemUserGroup Will not be serialized if unavailable. | 
| ValueList | A reference to a value list. Only available when StructureType = MFMetadataStructureItemValueList Will not be serialized if unavailable. | 
| ValueListItem | A reference to a value list item. Only available when StructureType = MFMetadataStructureItemValueListItem Will not be serialized if unavailable. | 
| View | A reference to a view. Only available when StructureType = MFMetadataStructureItemViewDef Will not be serialized if unavailable. | 
| Workflow | A reference to a workflow. Only available when StructureType = MFMetadataStructureItemWorkflow Will not be serialized if unavailable. |