Like XML, blockchains are kinda fundamentally misguided; they don't solve a problem that is actually important. XML solved syntax, which turned out not to be the problem. Blockchains [purport to] solve centralization, which will turn out not to be the problem.
This schema is currently referred to as "NISO Metadata for Images in XML (NISO MIX)". MIX is expressed using the XML schema language of the World Wide Web Consortium. MIX is maintained for NISO by the Network Development and MARC Standards Office of the Library of Congress with input from users.
This service lets you validate XML documents such as XHTML against the appropriate schemas. It performs a more accurate validation than the W3C validator.
W3C Schema can quickly become complex and difficult to determine if they are validating the correct vocabulary. The addition of embedded Schematron schema only makes this problem worse. Schema Unit Test (SUT) introduces a framework for testing XML Schema.
This framework has two parts.
The first is a namespace and vocabulary for embedding test cases into sample XML documents, designed to highlight what is legal and what is not legal in the vocabulary defined in the schema under test. This aspect is independent of what schema language is used and can in theory be applied to any schema language with automatic validation tools.
The second part is a Java implementation using JUnit for testing a W3C Schema with embedded Schematron schema. This implementation reads SUT test suite descriptions written in XML with embedded test cases as described above and then creates a JUnit test suite that can be executed inside JUnit in the usual way.