13. The relationship_ref element information item¶
relationship_ref element information items (referred to in this
specification as relationship_ref elements) are element information
items in the CellML namespace with local name equal to relationship_ref.
Every relationship_ref element MUST contain exactly one attribute
information item with local name relationship. This limit of one
attribute information item SHALL apply without regard to the
namespace in which the attribute information item is, and SHALL, to the
extent that it conflicts, override the ordinary rules for extension
information items.
In the event that the relationship attribute is in the empty
namespace, it MUST either take the value encapsulation or containment.
There MUST NOT exist a sibling relationship_ref element such that
the namespace of the relationship attribute on the sibling element
is identical to the namespace of the relationship attribute on this
element, and the value of the relationship attribute on the sibling
element is identical to the value of the relationship attribute on
this element.
A relationship_ref element MAY contain an attribute in the empty
namespace with local name name. In this case, it MUST NOT have a
relationship attribute in the empty namespace with value encapsulation.
The value of the name attribute MUST be a valid CellML identifier.