fieldset 

The fieldset element is used to group form fields.
      Only one legend element should occur in the content
      and if present should only be preceded by whitespace.

      NOTE: this content model is different from the XHTML 1.0 DTD,
      closer to the intended content model in HTML4 DTD

Element Information

Model

legend , (p | h1 | h2 | h3 | h4 | h5 | h6 | div | ul | ol | dl | pre | hr | blockquote | address | fieldset | table | form | a | br | span | bdo | map | object | img | tt | i | b | big | small | em | strong | dfn | code | q | samp | kbd | var | cite | abbr | acronym | sub | sup | input | select | textarea | label | button | noscript | ins | del | script)
Children: a, abbr, acronym, address, b, bdo, big, blockquote, br, button, cite, code, del, dfn, div, dl, em, fieldset, form, h1, h2, h3, h4, h5, h6, hr, i, img, input, ins, kbd, label, legend, map, noscript, object, ol, p, pre, q, samp, script, select, small, span, strong, sub, sup, table, textarea, tt, ul, var

Attributes

QName Type Fixed Default Use Inheritable Annotation
class xs:NMTOKENS optional
dir restriction of xs:token optional
id xs:ID optional
lang LanguageCode optional
onclick Script optional
ondblclick Script optional
onkeydown Script optional
onkeypress Script optional
onkeyup Script optional
onmousedown Script optional
onmousemove Script optional
onmouseout Script optional
onmouseover Script optional
onmouseup Script optional
style StyleSheet optional
title Text optional
xml:lang union of(xs:language, restriction of xs:string) optional 
Attempting to install the relevant ISO 2- and 3-letter
         codes as the enumerated possible values is probably never
         going to be a realistic possibility.  See
         RFC 3066 at http://www.ietf.org/rfc/rfc3066.txt and the IANA registry
         at http://www.iana.org/assignments/lang-tag-apps.htm for
         further information.

         The union allows for the 'un-declaration' of xml:lang with
         the empty string.

Used By

Element Group block

Source 

<xs:element name="fieldset">
  <xs:annotation>
    <xs:documentation>The fieldset element is used to group form fields. Only one legend element should occur in the content and if present should only be preceded by whitespace. NOTE: this content model is different from the XHTML 1.0 DTD, closer to the intended content model in HTML4 DTD</xs:documentation>
  </xs:annotation>
  <xs:complexType mixed="true">
    <xs:sequence>
      <xs:element ref="legend"/>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:group ref="block"/>
        <xs:element ref="form"/>
        <xs:group ref="inline"/>
        <xs:group ref="misc"/>
      </xs:choice>
    </xs:sequence>
    <xs:attributeGroup ref="attrs"/>
  </xs:complexType>
</xs:element>

Sample