...
If Fedora's logging level is set to DEBUG, Fedora also validates FOXML the XML object representation before committing it to permanent storage using both XSD and Schematron validation. This feature is intended to be used for testing Fedora.
...
Fedora Object validation is carried out prior to any object modifications being committed to permanent storage - if a modification would result in an invalid object according to the configured validators, the modification is not made and an error is reported.
By default, Fedora's configuration is to perform no object validation is performedupon modification operations.
In addition, objects can be validated on demand using the validate API method. This will validate objects according to their specificaiton specification using Enhanced Content Models.
...
Digital Object validation can be used to ensure that repository content conforms to the rules specified using Enhanced Content Models, which allows specification via an object's content model of XML datastream schema and relationships that should exist between objects.
To enable ECM object validation for every modification made to an object, uncomment the relevant sections in this file.
You can define your own validators for objects by writing Java classes that implement the org.fcrepo.server.validation.DOObjectValidator interface, and then adding these to the doobjectvalidator.xml Spring configuration file.If an API operation would result in an invalid object according to the configured validators, the API operation will not be performed, and an error will be reported.