[Property] mustContain [Values] Any valid RDF object reference, such as a URI or RDF ID. [Related Concepts] http://www.w3.org/2004/02/skos/core#subject OWL Cardinality http://www.w3.org/TR/owl-ref/#CardinalityRestriction [Description] 
A child element that must be contained by this role. For example a list must contain a listitem.