I use libxml2 to validate xmls with a schema, and because of some reasons I must use schema version 1.1, so I began my schema header like this:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning" elementFormDefault="qualified" attributeFormDefault="unqualified" vc:minVersion="1.1">

<xs:complexType name="test-type">
    <xs:all>
        <xs:element name="test"></xs:element>
        <xs:element name="test1" minOccurs="0" maxOccurs="4"></xs:element>
    </xs:all>
</xs:complexType>

xmlSchemaParseCtxtPtr ctxt;
xmlLineNumberDefault(1);
ctxt=xmlSchemaNewParserCtxt("schema.xsd");
_xmlSchema* _schema = xmlSchemaParse(ctxt);