imposes restrictions on the model, to ensure (for example) that the model will save data that matches the corresponding database table.
A model can validate data before passing it on to a data store such as a database to ensure that it conforms to the backend schema.
Since version 2.0, lxml.etree features pre-ISO-Schematron support, using the class lxml.etree.
This page describes the known error scenarios you may encounter while attempting to access a document in the viewer or while mass converting documents.
This guide also provides resolutions to those errors, where applicable.