DTD

computer science

Also known as: document type definition

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Last updated

July 16, 2026

Quick Summary

In computer science, a Document Type Definition (DTD) is a set of rules used to define the structure and elements of a document. DTDs are employed by markup languages like SGML and XML to specify what tags can be used and how they should be organized. This ensures consistency and allows software to correctly interpret and process the document's content. For example, a DTD might dictate that a document must have a title and that paragraphs can appear within table entries, but not vice versa. This enables parsing programs to validate document structure and other programs to prepare documents for display or indexing.123

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computer programming language
SGML
SGML is used to specify DTDs (document type definitions). A DTD defines a kind of document, such as a report, by specifying what elements must appear in the document—e.g., <Title>—and giving rules for the use of document elements, such as that a paragraph may appear within a table entry but…
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SGML is used to specify DTDs (document type definitions). A DTD defines a kind of document, such as a report, by specifying what elements must appear in the document—e.g., <Title>—and giving rules for the use of document elements, such as that a paragraph may appear within a table entry but…
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SGML
SGML is used to specify DTDs (document type definitions). A DTD defines a kind of document, such as a report, by specifying what elements must appear in the document—e.g., <Title>—and by giving rules for the use of document elements, such as that a paragraph may appear within a table entry…
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SGML is used to specify DTDs (document type definitions). A DTD defines a kind of document, such as a report, by specifying what elements must appear in the document—e.g., <Title>—and by giving rules for the use of document elements, such as that a paragraph may appear within a table entry…
Read More

XML
…SGML, XML uses DTDs (document type definitions) to define document types and the meanings of tags used in them. XML adopts conventions that make it easy to parse, such as that document entities are marked by both a beginning and an ending tag, such as <BEGIN>…</BEGIN>. XML provides more…
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…SGML, XML uses DTDs (document type definitions) to define document types and the meanings of tags used in them. XML adopts conventions that make it easy to parse, such as that document entities are marked by both a beginning and an ending tag, such as <BEGIN>…</BEGIN>. XML provides more…
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