http://www.w3.org/1999/xhtml
element h1

Model

<h1
  class = xs:NMTOKENS
  dir = <TODO local simpleType in attribute>
  id = xs:ID
  lang = LanguageCode
  lang = xs:language
  onclick = Script
  ondblclick = Script
  onkeydown = Script
  onkeypress = Script
  onkeyup = Script
  onmousedown = Script
  onmousemove = Script
  onmouseout = Script
  onmouseover = Script
  onmouseup = Script
  style = StyleSheet
  title = Text>
((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) ) | (ins | del | script) )*
</h1>

class

dir

id

lang

lang

In due course, we should install the relevant ISO 2- and 3-letter codes as the enumerated possible values . . .

onclick

ondblclick

onkeydown

onkeypress

onkeyup

onmousedown

onmousemove

onmouseout

onmouseover

onmouseup

style

title

Source

<xs:element name="h1">
  <xs:complexType mixed="true">
    <xs:complexContent mixed="true">
      <xs:extension base="Inline">
        <xs:attributeGroup ref="attrs"/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>
</xs:element>