Working with XML Catalogs
An XML Catalog maps a system ID or a URI reference pointing to a resource (stored either remotely or locally) to a local copy of the same resource. If XML processing relies on external resources (such as referenced schemas and stylesheets), the use of an XML Catalog becomes a necessity when Internet access is not available or the Internet connection is slow.
Oxygen XML Editor plugin supports any XML Catalog file that conforms to one of the following:
- OASIS XML Catalogs Committee Specification v1.1.
- OASIS Technical Resolution 9401:1997, including the plain-text flavor described in that resolution.
The version 1.1 of the OASIS XML Catalog specification introduces the possibility
to map a
system ID, public ID, or a URI to a local copy using only a suffix of the ID or URI
used in
the actual document. This is done using the catalog elements systemSuffix
and uriSuffix.
Depending on the resource type, Oxygen XML Editor plugin uses different catalog mappings.
Catalog Mappings
| Document | Referenced Resource | Mappings |
|---|---|---|
| XML | DTD | system or public
The Prefer option controls which one of the mappings should be used. |
| XML Schema |
The following strategy is used (if one step fails to provide a resource, the next is applied):
|
|
| Relax NG | ||
| Schematron | ||
| NVDL | ||
| XSL | XSL/ANY | URI |
| CSS | CSS | URI |
| XML Schema | XML Schema |
The following strategy is used (if one step fails to provide a resource, the next is applied):
|
| Relax NG | Relax NG |
Creating an XML Catalog with a Template
An XML Catalog file can be created quickly in Oxygen XML Editor plugin starting from the two XML Catalog document templates called OASIS XML Catalog 1.0 and OASIS XML Catalog 1.1 and available when creating new document templates.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE catalog
PUBLIC "-//OASIS//DTD XML Catalogs V1.1//EN"
"http://www.oasis-open.org/committees/entity/release/1.1/catalog.dtd">
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
<!-- Use "system" and "public" mappings when resolving DTDs -->
<system
systemId="http://www.docbook.org/xml/4.4/docbookx.dtd"
uri="frameworks/docbook/4.4/dtd/docbookx.dtd"/>
<!-- "systemSuffix" matches any system ID ending in a specified string -->
<systemSuffix
systemIdSuffix="docbookx.dtd"
uri="frameworks/docbook/dtd/docbookx.dtd"/>
<!-- Use "uri" for resolving XML Schema and XSLT stylesheets -->
<uri
name="http://www.oasis-open.org/docbook/xml/5.0/rng/docbook.rng"
uri="frameworks/docbook/5.0/rng/docbookxi.rng"/>
<!-- The "uriSuffix" matches any URI ending in a specified string -->
<uriSuffix
uriSuffix="docbook.xsl"
uri="frameworks/docbook/xsl/fo/docbook.xsl"/>
</catalog>
How Oxygen XML Editor plugin Determines which Catalog to Use
An XML catalog is used to resolve references for document validation and transformations and it maps such references to the built-in local copies of the schemas of the Oxygen XML Editor plugin frameworks (DocBook, DITA, TEI, XHTML, SVG, etc.)
Oxygen XML Editor plugin includes a built-in catalog set as default, but you can also create your own and Oxygen XML Editor plugin looks for catalogs in the following order:
- Global user-defined catalogs that are set in the XML Catalog preferences page.
- User-defined catalogs that are set at document type level, in the Catalog tab from the Document Type configuration dialog box.
- Default built-in catalogs.
An XML catalog can be used to map a W3C XML Schema specified with an URN in the
xsi:noNamespaceSchemaLocation attribute of an XML document to a local
copy of the schema.
Considering the following XML document code snippet:
<topic xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="urn:oasis:names:tc:dita:xsd:topic.xsd:1.1">
The URN can be resolved to a local schema file with a catalog entry like this:
<uri name="urn:oasis:names:tc:dita:xsd:topic.xsd:1.1"
uri="topic.xsd"/>