component element information items (referred to in this specification
as component elements) are element information items in the CellML
namespace with local name component, and which appear as a child of a
model element.
Every component element MUST contain a name attribute in the empty
namespace. The value of the name attribute MUST be a valid CellML
identifier. The value of the name attribute MUST NOT be identical to
the name attribute on any other component element or importcomponent
element in the CellML infoset.
A component element MAY contain zero or more specific information
item children, each of which MUST be of one of the following types:
A units element;
A variable element; or
An element information item in the MathML namespace, and with
local name math, which MUST be the top-level of a content MathML
tree, as described in MathML 2.0.