1  <grammar xmlns="http://relaxng.org/ns/structure/1.0">
 2    <start>
 3      <ref name="head"/>
 4    </start>
 5    <define name="head">
 6      <element name="head">
 7        <interleave>
 8          <ref name="title"/>
 9          <optional>
10            <ref name="base"/>
11          </optional>
12          <zeroOrMore>
13            <ref name="style"/>
14          </zeroOrMore>
15          <zeroOrMore>
16            <ref name="script"/>
17          </zeroOrMore>
18          <zeroOrMore>
19            <ref name="link"/>
20          </zeroOrMore>
21          <zeroOrMore>
22            <ref name="meta"/>
23          </zeroOrMore>
24        </interleave>
25      </element>
26    </define>
27    <define name="title">
28      <element name="title">
29        <text/>
30      </element>
31    </define>
32    <define name="base">
33      <element name="base">
34        <text/>
35      </element>
36    </define>
37    <define name="style">
38      <element name="style">
39        <text/>
40      </element>
41    </define>
42    <define name="script">
43      <element name="script">
44        <text/>
45      </element>
46    </define>
47    <define name="meta">
48      <element name="meta">
49        <text/>
50      </element>
51    </define>
52    <define name="link">
53      <element name="link">
54        <text/>
55      </element>
56    </define>
57  </grammar>