A document type definition (DTD) describes the tags that can be used in an XML file and indicates the valid arrangement of those tags. It can exist as a prologue to an XML file (internal DTD) or as a separate file (external DTD).
You can edit a DTD in the Source Editor by double-clicking its Explorer node or by right-clicking its node and choosing Edit. You can also view a DTD in the XML editor by right-clicking its node and choosing Open. However, the XML editor displays DTDs only in read-only form.
The contextual menu for external DTD nodes contains the following commands:
DTD objects are represented by the following nodes in the Explorer:
| Icon | Description | Properties |
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| Document type declaration (DTD) object |
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Element declaration category |
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| Element declaration |
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| Attribute declaration category |
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| Attribute declaration |
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| Attribute definition |
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| Entity declaration |
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Entity definition |
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| Notation declaration category |
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| Notation declaration |
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| Parameter entity declaration |
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