XML Catalog

XML Catalogs is a technique for replacement of external references in XML documents. This is checked when parsing the XML, if there is a substitution rule for the referenced external file in the catalog. Here is a matching rule is found, the existing in the file reference is replaced by the reference from the catalog. The catalog itself is an XML file that needs to be made ​​known to the parser. XML Catalogs is an OASIS standard.

XML Catalogs has two primary applications:

Examples

The following example shows a catalog (usually stored in a file called catalog.xml ), the http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict for the external reference with the system identifier. dtd a local DTD provides under dtd/xhtml1/xhtml1-strict.dtd. Similar procedure is followed with the two other DTDs.

          < system systemId = " http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd "              uri = " dtd/xhtml1/xhtml1-strict.dtd " />        < system systemId = " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd "              uri = " dtd/xhtml1/xhtml1-transitional.dtd " />        < system systemId = " http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd "              uri = " dtd/xhtml11/xhtml11-flat.dtd " />      < / catalog > The problem can also be solved for multiple documents by all parts of the URI will be replaced:

               < / catalog > The following catalog has different system identifiers (eg different spellings ) the same local DTD:

< DOCTYPE catalog PUBLIC "- / / OASIS / / DTD Entity Resolution XML Catalog V1.1 / / EN " " http://www.oasis-open.org/committees/entity/release/1.1/catalog.dtd " >   < / catalog > This functionality was only added with version 1.1 in the catalog standard.

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