Casa Robino

DTDs use a terse formal syntax that declares precisely which elements and references may appear where in the document of the particular type, and what the elements’ contents and attributes are. DTDs also declare entities which may be used in the instance document.<br />
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XML uses a subset of SGML DTD.<br />
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As of 2009[update] newer XML Namespace-aware schema languages (such as W3C XML Schema and ISO RELAX NG) have largely superseded DTDs.