| <?xml version="1.0" encoding="utf-8"?> | |
| <!--Arbortext, Inc., 1988-2005, v.4002--> | |
| <!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> | |
| <concept id="cdtdover" xml:lang="en-us"> | |
| <title>Document type definitions (DTDs) - overview</title> | |
| <titlealts> | |
| <searchtitle>Document type definition (DTD) - overview</searchtitle> | |
| </titlealts> | |
| <shortdesc>A document type definition (DTD) provides you with the means to | |
| validate XML files against a set of rules. When you create a DTD file, you | |
| can specify rules that control the structure of any XML files that reference | |
| the DTD file.</shortdesc> | |
| <prolog><metadata> | |
| <keywords><indexterm>DTD<indexterm>overview</indexterm></indexterm> | |
| </keywords> | |
| </metadata></prolog> | |
| <conbody> | |
| <p>A DTD can contain declarations that define elements, attributes, notations, | |
| and entities for any XML files that reference the DTD file. It also establishes | |
| constraints for how each element, attribute, notation, and entity can be used | |
| within any of the XML files that reference the DTD file.</p> | |
| <p>To be considered a valid XML file, the document must be accompanied by | |
| a DTD (or an XML schema), and conform to all of the declarations in the DTD | |
| (or XML schema).</p> | |
| <p>Certain XML parsers have the ability to read DTDs and check to see if the | |
| XML file it is reading follows all of those rules. While the parser is reading | |
| the XML file, it will check each line to be sure that it conforms to the rules | |
| that are laid out in the DTD file. If there is a problem, the parser generates | |
| an error and points to where the error occurs in the XML file. This kind of | |
| parser is called a validating parser because it validates the content of the | |
| XML file against the DTD.</p> | |
| </conbody> | |
| </concept> |