"In the text, gluons and intervals are presented as linear sequences with references. The schema shows all wscal components as recursive allowning infinite nesting. It might make sense to choose how the actual schedules are composed. If text is right, then an interval should not be able to contain a gluon.

For example, this is valid according to the schema:
<?xml version=""1.0"" encoding=""UTF-8""?>
<xcal:gluon xsi:schemaLocation=""urn:ietf:params:xml:ns:icalendar-2.0 iCalendar-wscal-extensions.xsd"" xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"" xmlns:xcal=""urn:ietf:params:xml:ns:icalendar-2.0"">
<xcal:properties/>
<xcal:components>
<xcal:gluon>
<xcal:properties></xcal:properties>
<xcal:components>
<xcal:interval>
<xcal:properties></xcal:properties>
<xcal:components></xcal:components>
</xcal:interval>
</xcal:components>
</xcal:gluon>
</xcal:components>
</xcal:gluon>"