001/*
002 * Copyright (c) 2004 World Wide Web Consortium,
003 *
004 * (Massachusetts Institute of Technology, European Research Consortium for
005 * Informatics and Mathematics, Keio University). All Rights Reserved. This
006 * work is distributed under the W3C(r) Software License [1] in the hope that
007 * it will be useful, but WITHOUT ANY WARRANTY; without even the implied
008 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
009 *
010 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
011 */
012
013package org.w3c.dom;
014
015/**
016 * The <code>Attr</code> interface represents an attribute in an 
017 * <code>Element</code> object. Typically the allowable values for the 
018 * attribute are defined in a schema associated with the document.
019 * <p><code>Attr</code> objects inherit the <code>Node</code> interface, but 
020 * since they are not actually child nodes of the element they describe, the 
021 * DOM does not consider them part of the document tree. Thus, the 
022 * <code>Node</code> attributes <code>parentNode</code>, 
023 * <code>previousSibling</code>, and <code>nextSibling</code> have a 
024 * <code>null</code> value for <code>Attr</code> objects. The DOM takes the 
025 * view that attributes are properties of elements rather than having a 
026 * separate identity from the elements they are associated with; this should 
027 * make it more efficient to implement such features as default attributes 
028 * associated with all elements of a given type. Furthermore, 
029 * <code>Attr</code> nodes may not be immediate children of a 
030 * <code>DocumentFragment</code>. However, they can be associated with 
031 * <code>Element</code> nodes contained within a 
032 * <code>DocumentFragment</code>. In short, users and implementors of the 
033 * DOM need to be aware that <code>Attr</code> nodes have some things in 
034 * common with other objects inheriting the <code>Node</code> interface, but 
035 * they also are quite distinct.
036 * <p>The attribute's effective value is determined as follows: if this 
037 * attribute has been explicitly assigned any value, that value is the 
038 * attribute's effective value; otherwise, if there is a declaration for 
039 * this attribute, and that declaration includes a default value, then that 
040 * default value is the attribute's effective value; otherwise, the 
041 * attribute does not exist on this element in the structure model until it 
042 * has been explicitly added. Note that the <code>Node.nodeValue</code> 
043 * attribute on the <code>Attr</code> instance can also be used to retrieve 
044 * the string version of the attribute's value(s).
045 * <p> If the attribute was not explicitly given a value in the instance 
046 * document but has a default value provided by the schema associated with 
047 * the document, an attribute node will be created with 
048 * <code>specified</code> set to <code>false</code>. Removing attribute 
049 * nodes for which a default value is defined in the schema generates a new 
050 * attribute node with the default value and <code>specified</code> set to 
051 * <code>false</code>. If validation occurred while invoking 
052 * <code>Document.normalizeDocument()</code>, attribute nodes with 
053 * <code>specified</code> equals to <code>false</code> are recomputed 
054 * according to the default attribute values provided by the schema. If no 
055 * default value is associate with this attribute in the schema, the 
056 * attribute node is discarded. 
057 * <p>In XML, where the value of an attribute can contain entity references, 
058 * the child nodes of the <code>Attr</code> node may be either 
059 * <code>Text</code> or <code>EntityReference</code> nodes (when these are 
060 * in use; see the description of <code>EntityReference</code> for 
061 * discussion). 
062 * <p>The DOM Core represents all attribute values as simple strings, even if 
063 * the DTD or schema associated with the document declares them of some 
064 * specific type such as tokenized. 
065 * <p>The way attribute value normalization is performed by the DOM 
066 * implementation depends on how much the implementation knows about the 
067 * schema in use. Typically, the <code>value</code> and 
068 * <code>nodeValue</code> attributes of an <code>Attr</code> node initially 
069 * returns the normalized value given by the parser. It is also the case 
070 * after <code>Document.normalizeDocument()</code> is called (assuming the 
071 * right options have been set). But this may not be the case after 
072 * mutation, independently of whether the mutation is performed by setting 
073 * the string value directly or by changing the <code>Attr</code> child 
074 * nodes. In particular, this is true when <a href='http://www.w3.org/TR/2004/REC-xml-20040204#dt-charref'>character 
075 * references</a> are involved, given that they are not represented in the DOM and they 
076 * impact attribute value normalization. On the other hand, if the 
077 * implementation knows about the schema in use when the attribute value is 
078 * changed, and it is of a different type than CDATA, it may normalize it 
079 * again at that time. This is especially true of specialized DOM 
080 * implementations, such as SVG DOM implementations, which store attribute 
081 * values in an internal form different from a string.
082 * <p>The following table gives some examples of the relations between the 
083 * attribute value in the original document (parsed attribute), the value as 
084 * exposed in the DOM, and the serialization of the value: 
085 * <table border='1' cellpadding='3'>
086 * <tr>
087 * <th>Examples</th>
088 * <th>Parsed 
089 * attribute value</th>
090 * <th>Initial <code>Attr.value</code></th>
091 * <th>Serialized attribute value</th>
092 * </tr>
093 * <tr>
094 * <td valign='top' rowspan='1' colspan='1'>
095 * Character reference</td>
096 * <td valign='top' rowspan='1' colspan='1'>
097 * <pre>"x&amp;#178;=5"</pre>
098 * </td>
099 * <td valign='top' rowspan='1' colspan='1'>
100 * <pre>"x\u00b2=5"</pre>
101 * </td>
102 * <td valign='top' rowspan='1' colspan='1'>
103 * <pre>"x&amp;#178;=5"</pre>
104 * </td>
105 * </tr>
106 * <tr>
107 * <td valign='top' rowspan='1' colspan='1'>Built-in 
108 * character entity</td>
109 * <td valign='top' rowspan='1' colspan='1'>
110 * <pre>"y&amp;lt;6"</pre>
111 * </td>
112 * <td valign='top' rowspan='1' colspan='1'>
113 * <pre>"y&lt;6"</pre>
114 * </td>
115 * <td valign='top' rowspan='1' colspan='1'>
116 * <pre>"y&amp;lt;6"</pre>
117 * </td>
118 * </tr>
119 * <tr>
120 * <td valign='top' rowspan='1' colspan='1'>Literal newline between</td>
121 * <td valign='top' rowspan='1' colspan='1'>
122 * <pre>
123 * "x=5&amp;#10;y=6"</pre>
124 * </td>
125 * <td valign='top' rowspan='1' colspan='1'>
126 * <pre>"x=5 y=6"</pre>
127 * </td>
128 * <td valign='top' rowspan='1' colspan='1'>
129 * <pre>"x=5&amp;#10;y=6"</pre>
130 * </td>
131 * </tr>
132 * <tr>
133 * <td valign='top' rowspan='1' colspan='1'>Normalized newline between</td>
134 * <td valign='top' rowspan='1' colspan='1'>
135 * <pre>"x=5 
136 * y=6"</pre>
137 * </td>
138 * <td valign='top' rowspan='1' colspan='1'>
139 * <pre>"x=5 y=6"</pre>
140 * </td>
141 * <td valign='top' rowspan='1' colspan='1'>
142 * <pre>"x=5 y=6"</pre>
143 * </td>
144 * </tr>
145 * <tr>
146 * <td valign='top' rowspan='1' colspan='1'>Entity <code>e</code> with literal newline</td>
147 * <td valign='top' rowspan='1' colspan='1'>
148 * <pre>
149 * &lt;!ENTITY e '...&amp;#10;...'&gt; [...]&gt; "x=5&amp;e;y=6"</pre>
150 * </td>
151 * <td valign='top' rowspan='1' colspan='1'><em>Dependent on Implementation and Load Options</em></td>
152 * <td valign='top' rowspan='1' colspan='1'><em>Dependent on Implementation and Load/Save Options</em></td>
153 * </tr>
154 * </table>
155 * <p>See also the <a href='http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407'>Document Object Model (DOM) Level 3 Core Specification</a>.
156 */
157public interface Attr extends Node {
158    /**
159     * Returns the name of this attribute. If <code>Node.localName</code> is 
160     * different from <code>null</code>, this attribute is a qualified name.
161     */
162    public String getName();
163
164    /**
165     *  <code>True</code> if this attribute was explicitly given a value in 
166     * the instance document, <code>false</code> otherwise. If the 
167     * application changed the value of this attribute node (even if it ends 
168     * up having the same value as the default value) then it is set to 
169     * <code>true</code>. The implementation may handle attributes with 
170     * default values from other schemas similarly but applications should 
171     * use <code>Document.normalizeDocument()</code> to guarantee this 
172     * information is up-to-date. 
173     */
174    public boolean getSpecified();
175
176    /**
177     * On retrieval, the value of the attribute is returned as a string. 
178     * Character and general entity references are replaced with their 
179     * values. See also the method <code>getAttribute</code> on the 
180     * <code>Element</code> interface.
181     * <br>On setting, this creates a <code>Text</code> node with the unparsed 
182     * contents of the string, i.e. any characters that an XML processor 
183     * would recognize as markup are instead treated as literal text. See 
184     * also the method <code>Element.setAttribute()</code>.
185     * <br> Some specialized implementations, such as some [<a href='http://www.w3.org/TR/2003/REC-SVG11-20030114/'>SVG 1.1</a>] 
186     * implementations, may do normalization automatically, even after 
187     * mutation; in such case, the value on retrieval may differ from the 
188     * value on setting. 
189     */
190    public String getValue();
191    /**
192     * On retrieval, the value of the attribute is returned as a string. 
193     * Character and general entity references are replaced with their 
194     * values. See also the method <code>getAttribute</code> on the 
195     * <code>Element</code> interface.
196     * <br>On setting, this creates a <code>Text</code> node with the unparsed 
197     * contents of the string, i.e. any characters that an XML processor 
198     * would recognize as markup are instead treated as literal text. See 
199     * also the method <code>Element.setAttribute()</code>.
200     * <br> Some specialized implementations, such as some [<a href='http://www.w3.org/TR/2003/REC-SVG11-20030114/'>SVG 1.1</a>] 
201     * implementations, may do normalization automatically, even after 
202     * mutation; in such case, the value on retrieval may differ from the 
203     * value on setting. 
204     * @exception DOMException
205     *   NO_MODIFICATION_ALLOWED_ERR: Raised when the node is readonly.
206     */
207    public void setValue(String value)
208                            throws DOMException;
209
210    /**
211     * The <code>Element</code> node this attribute is attached to or 
212     * <code>null</code> if this attribute is not in use.
213     * @since DOM Level 2
214     */
215    public Element getOwnerElement();
216
217    /**
218     *  The type information associated with this attribute. While the type 
219     * information contained in this attribute is guarantee to be correct 
220     * after loading the document or invoking 
221     * <code>Document.normalizeDocument()</code>, <code>schemaTypeInfo</code>
222     *  may not be reliable if the node was moved. 
223     * @since DOM Level 3
224     */
225    public TypeInfo getSchemaTypeInfo();
226
227    /**
228     *  Returns whether this attribute is known to be of type ID (i.e. to 
229     * contain an identifier for its owner element) or not. When it is and 
230     * its value is unique, the <code>ownerElement</code> of this attribute 
231     * can be retrieved using the method <code>Document.getElementById</code>
232     * . The implementation could use several ways to determine if an 
233     * attribute node is known to contain an identifier: 
234     * <ul>
235     * <li> If validation 
236     * occurred using an XML Schema [<a href='http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/'>XML Schema Part 1</a>]
237     *  while loading the document or while invoking 
238     * <code>Document.normalizeDocument()</code>, the post-schema-validation 
239     * infoset contributions (PSVI contributions) values are used to 
240     * determine if this attribute is a schema-determined ID attribute using 
241     * the <a href='http://www.w3.org/TR/2003/REC-xptr-framework-20030325/#term-sdi'>
242     * schema-determined ID</a> definition in [<a href='http://www.w3.org/TR/2003/REC-xptr-framework-20030325/'>XPointer</a>]
243     * . 
244     * </li>
245     * <li> If validation occurred using a DTD while loading the document or 
246     * while invoking <code>Document.normalizeDocument()</code>, the infoset <b>[type definition]</b> value is used to determine if this attribute is a DTD-determined ID 
247     * attribute using the <a href='http://www.w3.org/TR/2003/REC-xptr-framework-20030325/#term-ddi'>
248     * DTD-determined ID</a> definition in [<a href='http://www.w3.org/TR/2003/REC-xptr-framework-20030325/'>XPointer</a>]
249     * . 
250     * </li>
251     * <li> from the use of the methods <code>Element.setIdAttribute()</code>, 
252     * <code>Element.setIdAttributeNS()</code>, or 
253     * <code>Element.setIdAttributeNode()</code>, i.e. it is an 
254     * user-determined ID attribute; 
255     * <p ><b>Note:</b>  XPointer framework (see section 3.2 in [<a href='http://www.w3.org/TR/2003/REC-xptr-framework-20030325/'>XPointer</a>]
256     * ) consider the DOM user-determined ID attribute as being part of the 
257     * XPointer externally-determined ID definition. 
258     * </li>
259     * <li> using mechanisms that 
260     * are outside the scope of this specification, it is then an 
261     * externally-determined ID attribute. This includes using schema 
262     * languages different from XML schema and DTD. 
263     * </li>
264     * </ul>
265     * <br> If validation occurred while invoking 
266     * <code>Document.normalizeDocument()</code>, all user-determined ID 
267     * attributes are reset and all attribute nodes ID information are then 
268     * reevaluated in accordance to the schema used. As a consequence, if 
269     * the <code>Attr.schemaTypeInfo</code> attribute contains an ID type, 
270     * <code>isId</code> will always return true. 
271     * @since DOM Level 3
272     */
273    public boolean isId();
274
275}