XML data:
<Family>
<Father Firstname = "John" Familyname = "Smith" BirthDate = "1971-07-13" />
<Mother Firstname = "Jane" Familyname = "Smith" BirthDate = "1972-09-18" />
<Son Firstname = "Peter" Familyname = "Smith" BirthDate = "1997-01-18" />
<Daughter Firstname = "Mary" Familyname = "Smith" BirthDate = "1998-12-11" />
</Family>
The links point to the element models (see "ref" keywords in X-script). Note that the occurrence is specified in the corresponding X-script of an model:
<xd:def xmlns:xd = "http://www.xdef.org/xdef/4.2" root = "Family">
<Family>
<Father xd:script = "optional; ref Person;" />
<Mother xd:script = "required; ref Person;" />
<Son xd:script = "occurs *; ref Person;" />
<Daughter xd:script = "occurs *; ref Person;" />
</Family>
<Person Firstname = "string();" Familyname = "string();" BirthDate = "date();" />
</xd:def>
You can try it HERE