This allows you to make sure that the schema is valid and your instance documents are valid against the updated schema.
By default, the validation of a document is done by using a processor (XML parser, XSLT transformer, XQuery engine, etc.) to analyze the current file.
Some XML technologies are complicated, as is the case with XML Schema or XSLT processors.
When you edit documents that are intended to be public or should work no matter what engine is used, it is best to check them against all engines they will be used with.
pugixml is developed and maintained since 2006 and has many users.
All code is distributed under the MIT license, making it completely free to use in both open-source and proprietary applications.