/*
 * 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;

/**
 * The <code>Element</code> interface represents an element in an HTML or XML 
 * document. Elements may have attributes associated with them; since the 
 * <code>Element</code> interface inherits from <code>Node</code>, the 
 * generic <code>Node</code> interface attribute <code>attributes</code> may 
 * be used to retrieve the set of all attributes for an element. There are 
 * methods on the <code>Element</code> interface to retrieve either an 
 * <code>Attr</code> object by name or an attribute value by name. In XML, 
 * where an attribute value may contain entity references, an 
 * <code>Attr</code> object should be retrieved to examine the possibly 
 * fairly complex sub-tree representing the attribute value. On the other 
 * hand, in HTML, where all attributes have simple string values, methods to 
 * directly access an attribute value can safely be used as a convenience.In 
 * DOM Level 2, the method <code>normalize</code> is inherited from the 
 * <code>Node</code> interface where it was moved.
 * <p>See also the <a href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113'>Document Object Model (DOM) Level 2 Core Specification</a>.
 */
public interface Element extends Node {
    /**
     * The name of the element. For example, in: 
     * <pre> <elementExample 
     * id="demo"> ... </elementExample> , </pre>
     *  <code>tagName</code> has 
     * the value <code>"elementExample"</code>. Note that this is 
     * case-preserving in XML, as are all of the operations of the DOM. The 
     * HTML DOM returns the <code>tagName</code> of an HTML element in the 
     * canonical uppercase form, regardless of the case in the source HTML 
     * document.
     */
    public String getTagName();

    /**
     * Retrieves an attribute value by name.
     * @param name The name of the attribute to retrieve.
     * @return The <code>Attr</code> value as a string, or the empty string 
     *   if that attribute does not have a specified or default value.
     */
    public String getAttribute(String name);

    /**
     * Adds a new attribute. If an attribute with that name is already present 
     * in the element, its value is changed to be that of the value 
     * parameter. This value is a simple string; it is not parsed as it is 
     * being set. So any markup (such as syntax to be recognized as an 
     * entity reference) is treated as literal text, and needs to be 
     * appropriately escaped by the implementation when it is written out. 
     * In order to assign an attribute value that contains entity 
     * references, the user must create an <code>Attr</code> node plus any 
     * <code>Text</code> and <code>EntityReference</code> nodes, build the 
     * appropriate subtree, and use <code>setAttributeNode</code> to assign 
     * it as the value of an attribute.
     * <br>To set an attribute with a qualified name and namespace URI, use 
     * the <code>setAttributeNS</code> method.
     * @param name The name of the attribute to create or alter.
     * @param value Value to set in string form.
     * @exception DOMException
     *   INVALID_CHARACTER_ERR: Raised if the specified name contains an 
     *   illegal character.
     *   <br>NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     */
    public void setAttribute(String name, 
                             String value)
                             throws DOMException;

    /**
     * Removes an attribute by name. If the removed attribute is known to have 
     * a default value, an attribute immediately appears containing the 
     * default value as well as the corresponding namespace URI, local name, 
     * and prefix when applicable.
     * <br>To remove an attribute by local name and namespace URI, use the 
     * <code>removeAttributeNS</code> method.
     * @param name The name of the attribute to remove.
     * @exception DOMException
     *   NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     */
    public void removeAttribute(String name)
                                throws DOMException;

    /**
     * Retrieves an attribute node by name.
     * <br>To retrieve an attribute node by qualified name and namespace URI, 
     * use the <code>getAttributeNodeNS</code> method.
     * @param name The name (<code>nodeName</code>) of the attribute to 
     *   retrieve.
     * @return The <code>Attr</code> node with the specified name (
     *   <code>nodeName</code>) or <code>null</code> if there is no such 
     *   attribute.
     */
    public Attr getAttributeNode(String name);

    /**
     * Adds a new attribute node. If an attribute with that name (
     * <code>nodeName</code>) is already present in the element, it is 
     * replaced by the new one.
     * <br>To add a new attribute node with a qualified name and namespace 
     * URI, use the <code>setAttributeNodeNS</code> method.
     * @param newAttr The <code>Attr</code> node to add to the attribute list.
     * @return If the <code>newAttr</code> attribute replaces an existing 
     *   attribute, the replaced <code>Attr</code> node is returned, 
     *   otherwise <code>null</code> is returned.
     * @exception DOMException
     *   WRONG_DOCUMENT_ERR: Raised if <code>newAttr</code> was created from a 
     *   different document than the one that created the element.
     *   <br>NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     *   <br>INUSE_ATTRIBUTE_ERR: Raised if <code>newAttr</code> is already an 
     *   attribute of another <code>Element</code> object. The DOM user must 
     *   explicitly clone <code>Attr</code> nodes to re-use them in other 
     *   elements.
     */
    public Attr setAttributeNode(Attr newAttr)
                                 throws DOMException;

    /**
     * Removes the specified attribute node. If the removed <code>Attr</code> 
     * has a default value it is immediately replaced. The replacing 
     * attribute has the same namespace URI and local name, as well as the 
     * original prefix, when applicable.
     * @param oldAttr The <code>Attr</code> node to remove from the attribute 
     *   list.
     * @return The <code>Attr</code> node that was removed.
     * @exception DOMException
     *   NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     *   <br>NOT_FOUND_ERR: Raised if <code>oldAttr</code> is not an attribute 
     *   of the element.
     */
    public Attr removeAttributeNode(Attr oldAttr)
                                    throws DOMException;

    /**
     * Returns a <code>NodeList</code> of all descendant <code>Elements</code> 
     * with a given tag name, in the order in which they are encountered in 
     * a preorder traversal of this <code>Element</code> tree.
     * @param name The name of the tag to match on. The special value "*" 
     *   matches all tags.
     * @return A list of matching <code>Element</code> nodes.
     */
    public NodeList getElementsByTagName(String name);

    /**
     * Retrieves an attribute value by local name and namespace URI.
     * <br>Documents which do not support the "XML" feature will permit only 
     * the DOM Level 1 calls for creating/setting elements and attributes. 
     * Hence, if you specify a non-null namespace URI, these DOMs will never 
     * find a matching node.
     * @param namespaceURI The namespace URI of the attribute to retrieve.
     * @param localName The local name of the attribute to retrieve.
     * @return The <code>Attr</code> value as a string, or the empty string 
     *   if that attribute does not have a specified or default value.
     * @since DOM Level 2
     */
    public String getAttributeNS(String namespaceURI, 
                                 String localName);

    /**
     * Adds a new attribute. If an attribute with the same local name and 
     * namespace URI is already present on the element, its prefix is 
     * changed to be the prefix part of the <code>qualifiedName</code>, and 
     * its value is changed to be the <code>value</code> parameter. This 
     * value is a simple string; it is not parsed as it is being set. So any 
     * markup (such as syntax to be recognized as an entity reference) is 
     * treated as literal text, and needs to be appropriately escaped by the 
     * implementation when it is written out. In order to assign an 
     * attribute value that contains entity references, the user must create 
     * an <code>Attr</code> node plus any <code>Text</code> and 
     * <code>EntityReference</code> nodes, build the appropriate subtree, 
     * and use <code>setAttributeNodeNS</code> or 
     * <code>setAttributeNode</code> to assign it as the value of an 
     * attribute.
     * @param namespaceURI The namespace URI of the attribute to create or 
     *   alter.
     * @param qualifiedName The qualified name of the attribute to create or 
     *   alter.
     * @param value The value to set in string form.
     * @exception DOMException
     *   INVALID_CHARACTER_ERR: Raised if the specified qualified name 
     *   contains an illegal character, per the XML 1.0 specification .
     *   <br>NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     *   <br>NAMESPACE_ERR: Raised if the <code>qualifiedName</code> is 
     *   malformed per the Namespaces in XML specification, if the 
     *   <code>qualifiedName</code> has a prefix and the 
     *   <code>namespaceURI</code> is <code>null</code>, if the 
     *   <code>qualifiedName</code> has a prefix that is "xml" and the 
     *   <code>namespaceURI</code> is different from "
     *   http://www.w3.org/XML/1998/namespace", or if the 
     *   <code>qualifiedName</code>, or its prefix, is "xmlns" and the 
     *   <code>namespaceURI</code> is different from "
     *   http://www.w3.org/2000/xmlns/".
     *   <br>NOT_SUPPORTED_ERR: Always thrown if the current document does not 
     *   support the <code>"XML"</code> feature, since namespaces were 
     *   defined by XML.
     * @since DOM Level 2
     */
    public void setAttributeNS(String namespaceURI, 
                               String qualifiedName, 
                               String value)
                               throws DOMException;

    /**
     * Removes an attribute by local name and namespace URI. If the removed 
     * attribute has a default value it is immediately replaced. The 
     * replacing attribute has the same namespace URI and local name, as 
     * well as the original prefix.
     * <br>Documents which do not support the "XML" feature will permit only 
     * the DOM Level 1 calls for creating/setting elements and attributes. 
     * Hence, if you specify a non-null namespace URI, these DOMs will never 
     * find a matching node.
     * @param namespaceURI The namespace URI of the attribute to remove.
     * @param localName The local name of the attribute to remove.
     * @exception DOMException
     *   NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     * @since DOM Level 2
     */
    public void removeAttributeNS(String namespaceURI, 
                                  String localName)
                                  throws DOMException;

    /**
     * Retrieves an <code>Attr</code> node by local name and namespace URI.
     * <br>Documents which do not support the "XML" feature will permit only 
     * the DOM Level 1 calls for creating/setting elements and attributes. 
     * Hence, if you specify a non-null namespace URI, these DOMs will never 
     * find a matching node.
     * @param namespaceURI The namespace URI of the attribute to retrieve.
     * @param localName The local name of the attribute to retrieve.
     * @return The <code>Attr</code> node with the specified attribute local 
     *   name and namespace URI or <code>null</code> if there is no such 
     *   attribute.
     * @since DOM Level 2
     */
    public Attr getAttributeNodeNS(String namespaceURI, 
                                   String localName);

    /**
     * Adds a new attribute. If an attribute with that local name and that 
     * namespace URI is already present in the element, it is replaced by 
     * the new one.
     * @param newAttr The <code>Attr</code> node to add to the attribute list.
     * @return If the <code>newAttr</code> attribute replaces an existing 
     *   attribute with the same local name and namespace URI, the replaced 
     *   <code>Attr</code> node is returned, otherwise <code>null</code> is 
     *   returned.
     * @exception DOMException
     *   WRONG_DOCUMENT_ERR: Raised if <code>newAttr</code> was created from a 
     *   different document than the one that created the element.
     *   <br>NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
     *   <br>INUSE_ATTRIBUTE_ERR: Raised if <code>newAttr</code> is already an 
     *   attribute of another <code>Element</code> object. The DOM user must 
     *   explicitly clone <code>Attr</code> nodes to re-use them in other 
     *   elements.
     *   <br>NOT_SUPPORTED_ERR: Always thrown if the current document does not 
     *   support the <code>"XML"</code> feature, since namespaces were 
     *   defined by XML.
     * @since DOM Level 2
     */
    public Attr setAttributeNodeNS(Attr newAttr)
                                   throws DOMException;

    /**
     * Returns a <code>NodeList</code> of all the descendant 
     * <code>Elements</code> with a given local name and namespace URI in 
     * the order in which they are encountered in a preorder traversal of 
     * this <code>Element</code> tree.
     * <br>Documents which do not support the "XML" feature will permit only 
     * the DOM Level 1 calls for creating/setting elements and attributes. 
     * Hence, if you specify a non-null namespace URI, these DOMs will never 
     * find a matching node.
     * @param namespaceURI The namespace URI of the elements to match on. The 
     *   special value "*" matches all namespaces.
     * @param localName The local name of the elements to match on. The 
     *   special value "*" matches all local names.
     * @return A new <code>NodeList</code> object containing all the matched 
     *   <code>Elements</code>.
     * @since DOM Level 2
     */
    public NodeList getElementsByTagNameNS(String namespaceURI, 
                                           String localName);

    /**
     * Returns <code>true</code> when an attribute with a given name is 
     * specified on this element or has a default value, <code>false</code> 
     * otherwise.
     * @param name The name of the attribute to look for.
     * @return <code>true</code> if an attribute with the given name is 
     *   specified on this element or has a default value, <code>false</code>
     *    otherwise.
     * @since DOM Level 2
     */
    public boolean hasAttribute(String name);

    /**
     * Returns <code>true</code> when an attribute with a given local name and 
     * namespace URI is specified on this element or has a default value, 
     * <code>false</code> otherwise.
     * <br>Documents which do not support the "XML" feature will permit only 
     * the DOM Level 1 calls for creating/setting elements and attributes. 
     * Hence, if you specify a non-null namespace URI, these DOMs will never 
     * find a matching node.
     * @param namespaceURI The namespace URI of the attribute to look for.
     * @param localName The local name of the attribute to look for.
     * @return <code>true</code> if an attribute with the given local name 
     *   and namespace URI is specified or has a default value on this 
     *   element, <code>false</code> otherwise.
     * @since DOM Level 2
     */
    public boolean hasAttributeNS(String namespaceURI, 
                                  String localName);

}