http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
/*
 * Copyright (c) 2000 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.
 * See W3C License http://www.w3.org/Consortium/Legal/ for more details.
 */

package org.w3c.dom.css;

import org.w3c.dom.DOMException;


 The CSSRule interface is the abstract base interface for any 
type of CSS statement. This includes both rule sets and at-rules. An 
implementation is expected to preserve all rules specified in a CSS style 
sheet, even if the rule is not recognized by the parser. Unrecognized 
rules are represented using the CSSUnknownRule interface. 

See also the Document Object Model (DOM) Level 2 Style Specification.

Since:DOM Level 2
/**
 *  The <code>CSSRule</code> interface is the abstract base interface for any 
 * type of CSS statement. This includes both rule sets and at-rules. An 
 * implementation is expected to preserve all rules specified in a CSS style 
 * sheet, even if the rule is not recognized by the parser. Unrecognized 
 * rules are represented using the <code>CSSUnknownRule</code> interface. 
 * <p>See also the <a href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113'>Document Object Model (DOM) Level 2 Style Specification</a>.
 * @since DOM Level 2
 */
public interface CSSRule {
    // RuleType
    
The rule is a CSSUnknownRule.

/**
     * The rule is a <code>CSSUnknownRule</code>.
     */
    public static final short UNKNOWN_RULE              = 0;
    
The rule is a CSSStyleRule.

/**
     * The rule is a <code>CSSStyleRule</code>.
     */
    public static final short STYLE_RULE                = 1;
    
The rule is a CSSCharsetRule.

/**
     * The rule is a <code>CSSCharsetRule</code>.
     */
    public static final short CHARSET_RULE              = 2;
    
The rule is a CSSImportRule.

/**
     * The rule is a <code>CSSImportRule</code>.
     */
    public static final short IMPORT_RULE               = 3;
    
The rule is a CSSMediaRule.

/**
     * The rule is a <code>CSSMediaRule</code>.
     */
    public static final short MEDIA_RULE                = 4;
    
The rule is a CSSFontFaceRule.

/**
     * The rule is a <code>CSSFontFaceRule</code>.
     */
    public static final short FONT_FACE_RULE            = 5;
    
The rule is a CSSPageRule.

/**
     * The rule is a <code>CSSPageRule</code>.
     */
    public static final short PAGE_RULE                 = 6;

    
 The type of the rule, as defined above. The expectation is that 
binding-specific casting methods can be used to cast down from an 
instance of the CSSRule interface to the specific 
derived interface implied by the type. 

/**
     *  The type of the rule, as defined above. The expectation is that 
     * binding-specific casting methods can be used to cast down from an 
     * instance of the <code>CSSRule</code> interface to the specific 
     * derived interface implied by the <code>type</code>. 
     */
    public short getType();

    
 The parsable textual representation of the rule. This reflects the 
current state of the rule and not its initial value. 

/**
     *  The parsable textual representation of the rule. This reflects the 
     * current state of the rule and not its initial value. 
     */
    public String getCssText();
    
 The parsable textual representation of the rule. This reflects the 
current state of the rule and not its initial value. 

Throws:
  • DOMException – 
  SYNTAX_ERR: Raised if the specified CSS string value has a syntax 
  error and is unparsable.
  
    INVALID_MODIFICATION_ERR: Raised if the specified CSS string 
  value represents a different type of rule than the current one.
  
    HIERARCHY_REQUEST_ERR: Raised if the rule cannot be inserted at 
  this point in the style sheet.
  
    NO_MODIFICATION_ALLOWED_ERR: Raised if the rule is readonly.
/**
     *  The parsable textual representation of the rule. This reflects the 
     * current state of the rule and not its initial value. 
     * @exception DOMException
     *   SYNTAX_ERR: Raised if the specified CSS string value has a syntax 
     *   error and is unparsable.
     *   <br>INVALID_MODIFICATION_ERR: Raised if the specified CSS string 
     *   value represents a different type of rule than the current one.
     *   <br>HIERARCHY_REQUEST_ERR: Raised if the rule cannot be inserted at 
     *   this point in the style sheet.
     *   <br>NO_MODIFICATION_ALLOWED_ERR: Raised if the rule is readonly.
     */
    public void setCssText(String cssText)
                        throws DOMException;

    
 The style sheet that contains this rule. 

/**
     *  The style sheet that contains this rule. 
     */
    public CSSStyleSheet getParentStyleSheet();

    
 If this rule is contained inside another rule (e.g. a style rule 
inside an @media block), this is the containing rule. If this rule is 
not nested inside any other rules, this returns null. 

/**
     *  If this rule is contained inside another rule (e.g. a style rule 
     * inside an @media block), this is the containing rule. If this rule is 
     * not nested inside any other rules, this returns <code>null</code>. 
     */
    public CSSRule getParentRule();

}