Entire books have been written on meta-modeling. This section does not attempt to do complete justice to this topic.  However, it does overview some initial modeling thoughts on extending an implementation of the SID to include the dynamic addition of entities, meta-concepts (subclasses and attributes currently supported by the SID), associations, and association classes.<br/>A SID implementer can implement the models described in this section to rapidly adapt a database to changed information requirements without the need to make substantial changes to the database. At some point in time, the meta-data instances may be converted to explicitly modeled and implemented entities, subclasses, associations, association classes, and attributes.<br/>Some SID implementers may view meta-modeling associations as more an implementation view than an information view of entities and their associations. If the choice is that this is an implementation view then the model contained in this section can be placed in an implementation model rather than an information model.<br/><i>Note that Object (Instance) diagrams shown in this part of the guide book were not added to the SID model. They are included here for illustrative purposes only.</i><br/>Meta-modeling entities serve as the starting point that enables the dynamic addition of entities (classes and subclasses), eliminating the need to add them explicitly to an implementation of the SID. These entities can then be extended via the dynamic addition of attributes and associations.  The existing SID RootEntityType, which has been enhanced to support this capability, is shown the following Figure.<br/>