It defines annotations for customizing Java program elements to XML Schema mapping. V2.0 Metadata Schema has numerous extension points. AIF-RDF is the extended ontology represented in the Resource Description Framework Schema (RDFS) semantic language. The message exchange format is standardised as an XML schema (XSD). FIXML is an XML schema for FIX messages. JSON Schema is based on the concepts from XML Schema (XSD), but is JSON-based. There are several different languages available for specifying an XML schema. Some ASN.1 tools are able to translate between ASN.1 and XML schema (XSD). Each entry must have an objectClass attribute, containing named classes defined in the schema. DFDL achieves this by building upon the facilities of W3C XML Schema 1.0. NG provides for most of the advantages that W3C XML Schema does over DTDs. The DATA section contains application data according to one specific express schema. DQL statements are used for performing queries on the data within schema objects. A schema comprises a collection of schema objects. These integrity constraints ensure compatibility between parts of the schema.