I see that in Magento 2 all the xml (config, system, layout files, ...) files have a xsd associated for validation. This seams nice. Now you know what you are allowed to put in each file.
But I see that there are 2 validation schemas for each type of file.
system.xml for example.
The schema used inside the files is
app/code/Magento/Backend/etc/system_file.xsd but there is also
I found a reference to
Magento\Backend\Model\Config\SchemaLocator and it is declared as
system_file.xsd is called
The difference between the 2 files are minor.
Just some label differences and on one tag there is a
minoccurs="1" while on the other is
When is the
_schema file used? In this example