Looking through Magento 2
di.xml files there are various types of
When should we be using each schema?
It depends on the type of XML file you create.
Basically, all the XSD files can be found under the
lib/internal/Magento/Framework folder, here is the list on 2.1.2:
For example, if you create a
etc/acl.xml in your module, you'll have to use the
There are a few details about it in the official documentation:
My personal practice is: when I want to create an XML file, I check the same type of file in the core and get the URN schema from it.
Also, you can create your own XSD in case you want to use a custom type of XML: How can we write an XSD file in Magento 2?