What is it? UBL (Universal Business Language)?
Short answer
UBL (Universal Business Language) is international XML OASIS standard for exchange of business documents -invoices, credit cards, orders and more. For electronic invoicingcii This is a technical method for recording data which is defined in substance by the standard EN 16931. UBL is also a syntactic basis Peppol BIS Billing 3.0.
Not a European standard
UBL develop the international organisation OASIS, not the EU.
Not content of invoice
Contents EN 16931, UBL only method of entry into XML.
UBL 2. 1 XSD
Peppol BIS Billing 3.0 has no own XSD, builds on UBL 2.1.
Other format, same content
CII writes the same Business Terms to another XML structure.
Conclusion
UBL is the technical language of the registration e-invoice to XML; content determines EN 16931 and network usage rules Peppol Supplement Peppol BIS Billing 3.0.
Not legal advice. Machine-translated answer, not yet manually reviewed. For the exact wording, see the Slovak original.