In order to provide better model flexibility, some models allow adding extensions, which could serve specific use cases. Usage of extension is always optional and helps to add particular feature to the framework without changing it.
- MedBiquitous schemas may include an extensibility points to allow members to address situations where the standard format is insufficient to meet some special need.
- The HR-XML Europass CV Application profile and more other all HR-XML schemas allow to use wildcard extensions in many places called "UserArea" in the specifications.
InLOC allows extension through 3 mechanisms.
- Other Simple atomic properties not specified in InLOC may be added, in a different namespace, to extend the information represented about a LOCdefinition or a LOCstructure. If an XSD is used to check validity, all the extra elements would need to be added.
- Other types may be defined by other authorities, and given appropriate HTTP URIs for the type.
- Other LOCassociationships may be defined by other authorities, and given appropriate HTTP URIs for the hasScheme.id.
In both the last two cases, any XSD would need to be modified to include the new type terms.