XML’s ability to represent both hierarchies and references spanning hierarchies is attractive. XML is also attractive because standard tools (parsers and editors with a parser inside) can be used to validate models; no new code may need necessarily to be created. The document-type or schema description lies outside the program. As the following articles demonstrate, multiple DTDs and schemas for representing music are already in use.
Among its other strengths, XML is easy to learn because it has the same “look and feel” as HTML, the current formatting language of World Wide Web documents. While other markup languages and formats claim to be easy to learn, XML is designed to facilitate rapid development of related tools and to be accessible in any modern programming language. Free XML syntax-checking tools are available to check the validity of a document without knowing what it means.