title: What is the typical maximum length of values of the XML/XSD ID/IDREF types?
body: <p>The <a href="http://www.w3.org/TR/xmlschema-2/" rel="nofollow">W3C XSD 1.0 Part 2: Datatypes</a> specification refers to the <a href="http://www.w3.org/TR/xml/" rel="nofollow">W3C XML 1.0</a> specification for the definition of the ID and IDREF types, but none of these documents defines any constraints on the length of values of these types.</p>
  
  <p>However, it seems that some XML editors implement length limitations for these types.</p>
  
  <p>Also, some Web browsers seem to implement length limitations, e.g. on the "id" attribute of the HTML Hx elements (which is defined as XML ID type in both HTML 4 and XHTML 1.1).</p>
  
  <ol>
  <li><p>Are there any constraints on the length of the ID/IDREF types defined by a W3C specification or some other specification ?</p></li>
  <li><p>What are typical length constraints implemented by XML editors ?</p></li>
  <li><p>What are typical length constraints implemented by Web browsers (for HTML) ?</p></li>
  </ol>