Rules from the original specification possibly not included

[jonc125]

We may or may not want to include each of these somewhere.

• The definitions of quantitative & qualitative models, conformance levels, and the term "for interoperability"
• 2.4.3 bullet 3 (extension elements cannot contain content in the CellML namespace)
• 2.5.2 (but this rule conflicts with the namespaces in XML recommendation, so should be dropped)
• 3.4.5.4 bullet 2 (each map_components element must declare a unique pair of components to connect)
• 4.2.1 "CellML processing software must interpret MathML elements according to the semantics defined in the MathML 2.0 Recommendation."
• 4.2.3 (the CellML subset of MathML)
• 5.5.2 (Units associated with the MathML constants elements)
• 6.4.3.2 bullet 1 (I think the normative spec makes all relationships hierarchical)
• Section 7 (reactions)