Every form in this example is surrounded by a content box.
The submit buttons in the inner forms only put the inner value into the model.
The submit button in the outer form put all values into the model.
The validation for the inner value 2 and for the outer value is activated, both fields are required.
<tc:box label="Outer Form">
<tc:form>
<tc:box label="Inner Form 1">
<tc:form>
<tc:in label="Inner Value 1"/>
<tc:out label="Inner Value 1 in Model"/>
<tc:button label="Submit"/>
</tc:form>
</tc:box>
<tc:box label="Inner Form 2">
...
</tc:box>
<tc:separator/>
<tc:in label="Outer Value" required="true"/>
<tc:out label="Outer Value in Model"/>
<tc:button label="Submit"/>
</tc:form>
</tc:box>