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The structure of an XML document and the required restrictions on its elements and their attributes are defined with an XML schema. This makes it easier to edit XML documents in a visual editor. For more information about schema association, see Associating a Schema to XML Documents. The Author mode renders the content of the XML documents visually, based on a CSS stylesheet associated with the document.

Associating a Stylesheet with an XML Document

The rendering of an XML document in the Author mode is driven by a CSS stylesheet that conforms to the version 2.1 of the CSS specification from the W3C consortium. Some CSS 3 features, such as namespaces and custom extensions, of the CSS specification are also supported. Oxygen XML Editor also supports stylesheets coded with the LESS dynamic stylesheet language.

There are several methods for associating a stylesheet (CSS or LESS) with an XML document:
  1. Insert the xml-stylesheet processing instruction with the type attribute at the beginning of the XML document. If you do not want to alter your XML documents, you should create a new document type (framework).
    CSS example:
    <?xml-stylesheet type="text/css" href="test.css"?>
    LESS example:
    <?xml-stylesheet type="text/css" href="test.less"?> 
    Note: XHTML documents need a link element, with the href and type attributes in the head child element, as specified in the W3C CSS specification. XHTML example:
    <link href="/style/screen.css" rel="stylesheet" type="text/css"/>
    Tip: You can also insert the xml-stylesheet processing instruction by using the Associate XSLT/CSS Stylesheet action that is available on the toolbar or in the Document > XML Document menu.
  2. Add a new CSS or LESS file to a framework (document type). To do so, open the Preferences dialog box (Options > Preferences) and go to Document Type Association. Edit the appropriate framework, open the Author tab, then the CSS subtab. Press the New button to add a new CSS or LESS file.
    Note: The predefined frameworks are read-only, so you need to Extend or Duplicate them to configure them as custom frameworks.

You can read more about associating a CSS to a document type in Customizing the Main CSS of a Framework.

If a document has no CSS association or the referenced stylesheet files cannot be loaded, a default one is used. A warning message is also displayed at the beginning of the document, presenting the reason why the CSS cannot be loaded.

Figure: Document with no CSS association default rendering

Selecting and Combining Multiple CSS Styles

Oxygen XML Editor provides a Styles drop-down menu on the toolbar that allows you to select one main (non-alternate) CSS style and multiple alternate CSS styles. This makes it easy to change the look of the document as it appears in Author mode and the output without having to continually edit the CSS stylesheets.

Tip: For information about configuring the Styles drop-down menu, see Configuring and Managing Multiple CSS Styles.

You can select a main CSS style that applies to the whole document and then alternate styles that are applied as layers to specific parts of the document. For example, in the subsequent figure, a DITA document has the Century style selected for the main CSS and the alternate styles Full width, Show table column specification, Hints, and Inline actions are combined for additive styling to specific parts of the document.

The selections from the Styles drop-down menu are persistent, meaning that Oxygen XML Editor will remember the selections when subsequent documents are opened.

Figure: Styles Drop-down Menu in a DITA Document