cellml_1_0.rng

<?xml version="1.0" encoding="UTF-8"?>
<!--
  RELAX NG schema for CellML 1.0
  Author: Jonathan Cooper
  Initial version created using Trang, and then modified
  for correctness and legibility.
-->
<!--
  TODO:
   - Tidy metadata checking
-->
<!-- Core CellML namespaces -->
<!-- Metadata-related namespaces -->
<!-- Our extension namespaces (URIs will change) -->
<!--
  The 'no namespace' namespace, which is what will get used for
  most CellML attributes. Note the spec is broken in rule 2.5.2.
-->
<grammar xmlns:cellml="http://www.cellml.org/cellml/1.0#"
         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
         xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:mathml="http://www.w3.org/1998/Math/MathML"
         xmlns:cmeta="http://www.cellml.org/metadata/1.0#"
         xmlns="http://relaxng.org/ns/structure/1.0"
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
  <!--
    Some general notes:
     - rule 2.5.2 conflicts with the standard interpretation of XML namespaces.  Oops
     - No CellML elements contain text content
  -->
  <!--
    Valid CellML identifiers (rule 2.4.1)
    This is quite complex to get right.  The natural choice might
    be xsd:ID, but the lexical space isn't that of NCName: identifiers
    may start with a digit (yuck) and may not contain '.'.  Also
    identifiers are not always unique across a document (use the
    cmeta:id attribute for unique IDs).
  -->
  <define name="ident">
    <data type="token">
      <param name="pattern">_*[0-9a-zA-Z][_0-9a-zA-Z]*</param>
    </data>
  </define>
  <define name="oxygen-fix">
    <empty/>
  </define>
  <!-- Work around oXygen's parser getting confused by the regexp above -->
  <!--
    Extension namespaces are allowed (rule 2.4.3)
    Foreign elements should not contain CellML elements or attributes. We disallow this entirely,
    for technical reasons (id attribute conflicts).
  -->
  <define name="foreign-nodes">
    <zeroOrMore>
      <choice>
        <ref name="foreign-attributes-non-local"/>
        <ref name="foreign-elements"/>
      </choice>
    </zeroOrMore>
  </define>
  <define name="foreign-elements">
    <zeroOrMore>
      <element>
        <anyName>
          <except>
            <nsName ns="http://www.cellml.org/cellml/1.0#"/>
            <nsName ns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"/>
            <nsName ns="http://www.w3.org/1998/Math/MathML"/>
          </except>
        </anyName>
        <zeroOrMore>
          <choice>
            <zeroOrMore>
              <ref name="foreign-elements"/>
            </zeroOrMore>
            <zeroOrMore>
              <ref name="foreign-attributes"/>
            </zeroOrMore>
            <text/>
          </choice>
        </zeroOrMore>
      </element>
    </zeroOrMore>
  </define>
  <define name="foreign-attributes-non-local">
    <zeroOrMore>
      <attribute>
        <anyName>
          <except>
            <nsName ns="http://www.cellml.org/cellml/1.0#"/>
            <nsName ns=""/>
            <name>cmeta:id</name>
          </except>
        </anyName>
      </attribute>
    </zeroOrMore>
  </define>
  <define name="foreign-attributes">
    <zeroOrMore>
      <attribute>
        <anyName>
          <except>
            <nsName ns="http://www.cellml.org/cellml/1.0#"/>
            <name>cmeta:id</name>
          </except>
        </anyName>
      </attribute>
    </zeroOrMore>
  </define>
  <!--
    All CellML elements may take this attribute, so that they can be
    referred to by metadata.
  -->
  <define name="cmeta.id">
    <optional>
      <attribute name="cmeta:id">
        <data type="ID"/>
      </attribute>
    </optional>
  </define>
  <!--
    Nodes that are common to every CellML element.
    Wrap these in parens so they're easier to add in.
  -->
  <define name="common-nodes">
    <interleave>
      <ref name="foreign-nodes"/>
      <ref name="cmeta.id"/>
      <zeroOrMore>
        <ref name="rdf.RDF"/>
      </zeroOrMore>
    </interleave>
  </define>
  <start>
    <ref name="cellml.model"/>
  </start>
  <define name="cellml.model">
    <element name="cellml:model">
      <interleave>
        <!-- Every model needs a name -->
        <attribute name="name">
          <ref name="ident"/>
        </attribute>
        <zeroOrMore>
          <!--
            Elements may appear in any order, although that given here
            is recommended for CellML elements (rule 3.4.1).
          -->
          <ref name="cellml.units"/>
        </zeroOrMore>
        <zeroOrMore>
          <ref name="cellml.component"/>
        </zeroOrMore>
        <zeroOrMore>
          <ref name="cellml.group"/>
        </zeroOrMore>
        <zeroOrMore>
          <ref name="cellml.connection"/>
        </zeroOrMore>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- CellML components (rule 3.4.2) -->
  <define name="cellml.component">
    <element name="cellml:component">
      <interleave>
        <!-- Every component needs a (unique) name -->
        <attribute name="name">
          <ref name="ident"/>
        </attribute>
        <zeroOrMore>
          <!-- Again, order is not required, but is recommended. -->
          <ref name="cellml.units"/>
        </zeroOrMore>
        <zeroOrMore>
          <ref name="cellml.variable"/>
        </zeroOrMore>
        <zeroOrMore>
          <!--
            The use of multiple reaction elements is allowed but
            discoraged (7.4.1.1).
          -->
          <ref name="cellml.reaction"/>
        </zeroOrMore>
        <zeroOrMore>
          <ref name="mathml.math"/>
        </zeroOrMore>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- CellML variables (rule 3.4.3) -->
  <define name="cellml.variable">
    <element name="cellml:variable">
      <!--
        Each variable needs a name, which is unique within
        the owning component (but not necessarily across a
        whole model). 3.4.3.2
      -->
      <attribute name="name">
        <ref name="ident"/>
      </attribute>
      <!--
        Every variable must declare its units.
        This must be an identifier (5.4.2) corresponding to one
        of the standard units or a user-defined unit within the
        current model or component (3.4.3.3).
      -->
      <attribute name="units">
        <ref name="ident"/>
      </attribute>
      <!--
        Interface values are optional, and can be one of
        "in", "out" or "none" (default) (3.4.3.4 & 3.4.3.5).
        They cannot both be "in" (4.3.4.6).
      -->
      <choice>
        <group>
          <attribute name="private_interface">
            <value>in</value>
          </attribute>
          <optional>
            <attribute name="public_interface">
              <choice>
                <value>out</value>
                <value>none</value>
              </choice>
            </attribute>
          </optional>
        </group>
        <group>
          <attribute name="public_interface">
            <value>in</value>
          </attribute>
          <optional>
            <attribute name="private_interface">
              <choice>
                <value>out</value>
                <value>none</value>
              </choice>
            </attribute>
          </optional>
        </group>
        <group>
          <optional>
            <attribute name="private_interface">
              <choice>
                <value>out</value>
                <value>none</value>
              </choice>
            </attribute>
          </optional>
          <optional>
            <attribute name="public_interface">
              <choice>
                <value>out</value>
                <value>none</value>
              </choice>
            </attribute>
          </optional>
          <optional>
            <!--
              An initial value must be a real number (3.4.3.7) and
              may not be defined on a variable which has either
              interface set to "in" (3.4.3.8)
            -->
            <attribute name="initial_value">
              <data type="double"/>
            </attribute>
          </optional>
        </group>
      </choice>
      <ref name="common-nodes"/>
    </element>
  </define>
  <!--
    The CellML connection element specifies maps between variables
    in different components.
    See rules 3.4.4, 3.4.5
  -->
  <define name="cellml.connection">
    <element name="cellml:connection">
      <interleave>
        <!-- Again order of elements is non-essential but recommended (3.4.4.1) -->
        <!-- There must be exactly one map_components element (3.4.4.1) -->
        <element name="cellml:map_components">
          <!--
            Components to map between must be specified (3.4.5.1).
            They must refer to distinct (3.4.5.4) components within
            the current model (3.4.5.2 & 3.4.5.3).
            There must also be at most one connection between any 2 given
            components.
          -->
          <attribute name="component_1">
            <ref name="ident"/>
          </attribute>
          <attribute name="component_2">
            <ref name="ident"/>
          </attribute>
          <ref name="common-nodes"/>
        </element>
        <oneOrMore>
          <!-- There must be at least one map_variables element (3.4.4.1) -->
          <element name="cellml:map_variables">
            <!--
              Variables to map must be specified (3.4.6.1).
              The variable_1 attribute must equal the name of a variable
              defined within component_1 (3.4.6.2); similarly for
              variable_2 (3.4.6.3).
              Allowed mappings are determined by the encapsulation
              hierarchy (3.4.6.4), which is beyond the scope of RELAX NG.
            -->
            <attribute name="variable_1">
              <ref name="ident"/>
            </attribute>
            <attribute name="variable_2">
              <ref name="ident"/>
            </attribute>
            <ref name="common-nodes"/>
          </element>
        </oneOrMore>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- User-defined units (see section 5 of the specification). -->
  <define name="cellml.units">
    <element name="cellml:units">
      <interleave>
        <!--
          All units must be named (5.4.1.1).
          The name must not be equal one of the names defined in the
          standard dictionary of units.  It must also be unique across
          all units within its parent element. (5.4.1.2)
        -->
        <attribute name="name">
          <ref name="ident"/>
        </attribute>
        <ref name="common-nodes"/>
        <choice>
          <!--
            If the base_units attribute has the value "yes" then only
            foreign or metadata content is allowed (5.4.1.1).
          -->
          <attribute name="base_units">
            <value>yes</value>
          </attribute>
          <interleave>
            <optional>
              <!--
                If base_units is defined as "no" or is unspecified (5.4.1.3)
                then the unit element must contain at least one units element
                (5.4.1.1).
              -->
              <attribute name="base_units">
                <value>no</value>
              </attribute>
            </optional>
            <choice>
              <oneOrMore>
                <!-- Complex units definition, or simple units without offset -->
                <element name="cellml:unit">
                  <!--
                    All unit elements must define a units attribute (5.4.2.1),
                    which must reference a valid units name (5.4.2.2).
                    Circular definitions are not allowed.
                  -->
                  <attribute name="units">
                    <ref name="ident"/>
                  </attribute>
                  <optional>
                    <!--
                      The prefix, if present, must be an integer or a standard
                      prefix name (e.g. centi, which is equivalent to -2).  The
                      default is 0. (5.4.2.3)
                    -->
                    <attribute name="prefix">
                      <choice>
                        <data type="integer"/>
                        <ref name="prefix-name"/>
                      </choice>
                    </attribute>
                  </optional>
                  <optional>
                    <!--
                      The exponent, if present, must be a real number, and
                      defaults to 1.0. (5.4.2.4)
                    -->
                    <attribute name="exponent">
                      <data type="double"/>
                    </attribute>
                  </optional>
                  <optional>
                    <!--
                      The multiplier, if present, must be a real number, and
                      defaults to 1.0. (5.4.2.5)
                    -->
                    <attribute name="multiplier">
                      <data type="double"/>
                    </attribute>
                  </optional>
                  <optional>
                    <!--
                      The offset, if present, must be a real number, and
                      defaults to 0.0. (5.4.2.6)
                      It must be omitted or zero except in a simple units
                      definition (5.4.2.7).
                    -->
                    <attribute name="offset">
                      <value type="decimal">0.0</value>
                    </attribute>
                  </optional>
                  <ref name="common-nodes"/>
                </element>
              </oneOrMore>
              <!--
                Simple units definition with offset (5.4.2.7)
                These have a non-zero value for the offset attribute, and
                only a single unit element.
              -->
              <element name="cellml:unit">
                <!--
                  All unit elements must define a units attribute (5.4.2.1),
                  which must reference a valid units name (5.4.2.2).
                  Circular definitions are not allowed.
                -->
                <attribute name="units">
                  <ref name="ident"/>
                </attribute>
                <optional>
                  <!--
                    The prefix, if present, must be an integer or a standard
                    prefix name (e.g. centi, which is equivalent to -2).  The
                    default is 0. (5.4.2.3)
                  -->
                  <attribute name="prefix">
                    <choice>
                      <data type="integer"/>
                      <ref name="prefix-name"/>
                    </choice>
                  </attribute>
                </optional>
                <optional>
                  <!--
                    The exponent, if present, must be a real number, and
                    defaults to 1.0. (5.4.2.4)
                    It must be 1.0 if offset is non-zero (5.4.2.7).
                  -->
                  <attribute name="exponent">
                    <value type="double">1.0</value>
                  </attribute>
                </optional>
                <optional>
                  <!--
                    The multiplier, if present, must be a real number, and
                    defaults to 1.0. (5.4.2.5)
                  -->
                  <attribute name="multiplier">
                    <data type="double"/>
                  </attribute>
                </optional>
                <optional>
                  <!--
                    The offset, if present, must be a real number, and
                    defaults to 0.0. (5.4.2.6)
                    It must be omitted or zero except in a simple units
                    definition (5.4.2.7).
                  -->
                  <attribute name="offset">
                    <data type="decimal">
                      <except>
                        <value type="decimal">0.0</value>
                      </except>
                    </data>
                  </attribute>
                </optional>
                <ref name="common-nodes"/>
              </element>
            </choice>
          </interleave>
        </choice>
      </interleave>
    </element>
  </define>
  <!--
    The set of names that may be used in the prefix attribute on a
    unit element.
  -->
  <define name="prefix-name">
    <choice>
      <value>yotta</value>
      <value>zetta</value>
      <value>exa</value>
      <value>peta</value>
      <value>tera</value>
      <value>giga</value>
      <value>mega</value>
      <value>kilo</value>
      <value>hecto</value>
      <value>deka</value>
      <value>deci</value>
      <value>centi</value>
      <value>milli</value>
      <value>micro</value>
      <value>nano</value>
      <value>pico</value>
      <value>femto</value>
      <value>atto</value>
      <value>zepto</value>
      <value>yocto</value>
    </choice>
  </define>
  <!-- Groups (see section 6 of the specification) -->
  <define name="cellml.group">
    <element name="cellml:group">
      <interleave>
        <oneOrMore>
          <!-- See 6.4.1.1 -->
          <ref name="cellml.relationship_ref"/>
        </oneOrMore>
        <oneOrMore>
          <ref name="cellml.component_ref"/>
        </oneOrMore>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- 6.4.2: the relationship_ref element -->
  <define name="cellml.relationship_ref">
    <element name="cellml:relationship_ref">
      <interleave>
        <!--
          There must be a relationship attribute, either in the 'CellML
          namespace' (meaning no NS) or a user namespace (6.4.2.1)
          I haven't figured out how to describe user-defined relationships
          yet.  The best way may be to make the relationship attr optional,
          but this would then allow invalid models.  TODO
          For the CellML namespace case, the value must be "containment" or
          "encapsulation" (6.4.2.2)
        -->
        <choice>
          <attribute name="relationship">
            <value>encapsulation</value>
          </attribute>
          <group>
            <!--
              For a non-encapsulation relationship, a name attribute is also
              permitted (6.4.2.3) to name a hierarchy.
            -->
            <attribute name="relationship">
              <value>containment</value>
            </attribute>
            <optional>
              <attribute name="name">
                <ref name="ident"/>
              </attribute>
            </optional>
          </group>
        </choice>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- 6.4.3: the component_ref element -->
  <define name="cellml.component_ref">
    <element name="cellml:component_ref">
      <interleave>
        <!--
          The component attribute is mandatory; child elements are optional
          (6.4.3.1).
          The value of the component attribute should be the name of a
          component defined in the current model (6.4.3.3)
          The restrictions of 6.4.3.2 cannot be adequately expressed in
          RELAX NG.
        -->
        <attribute name="component">
          <ref name="ident"/>
        </attribute>
        <zeroOrMore>
          <ref name="cellml.component_ref"/>
        </zeroOrMore>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- Reactions (see section 7 of the specification) -->
  <define name="cellml.reaction">
    <element name="cellml:reaction">
      <interleave>
        <optional>
          <!--
            There may be a reversible attribute, which can take the values
            "yes" or "no", and defaults to "yes" (7.4.1.2).  It is recommended
            to always specify a value.
          -->
          <attribute name="reversible">
            <choice>
              <value>yes</value>
              <value>no</value>
            </choice>
          </attribute>
        </optional>
        <oneOrMore>
          <!--
            The recommended best practice is to define one variable_ref
            element for each variable representing a chemical species that
            participates in the reaction, and one variable_ref element for
            the variable representing the rate of the reaction (7.4.1.1)
          -->
          <ref name="cellml.variable_ref"/>
        </oneOrMore>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!-- 7.4.2: the variable_ref element -->
  <define name="cellml.variable_ref">
    <element name="cellml:variable_ref">
      <interleave>
        <!--
          The variable attribute must have a value equal to the name of
          a variable defined in the current component (7.4.2.2).  A
          variable must only be referenced once in a given reaction.
        -->
        <attribute name="variable">
          <ref name="ident"/>
        </attribute>
        <!--
          There must be at least one role element (7.4.2.1).  The
          recommended best practice is to define one role element for
          each role assumed by the chemical species represented by the
          referenced variable.
        -->
        <choice>
          <oneOrMore>
            <element name="cellml:role">
              <choice>
                <group>
                  <!-- The role attribute must take one of 7 values (7.4.3.2) -->
                  <attribute name="role">
                    <choice>
                      <value>catalyst</value>
                      <value>activator</value>
                      <value>inhibitor</value>
                      <value>modifier</value>
                    </choice>
                    <!-- Some unspecified effect -->
                  </attribute>
                  <optional>
                    <!--
                      The direction attribute defaults to "forward" (7.4.3.4),
                      indicating the role of this variable when the reaction
                      is running in the favoured direction.
                    -->
                    <attribute name="direction">
                      <choice>
                        <value>forward</value>
                        <value>reverse</value>
                        <value>both</value>
                      </choice>
                    </attribute>
                  </optional>
                  <optional>
                    <!--
                      Usually this will be an integer, but fractional values
                      are allowed (7.4.3.6).
                    -->
                    <attribute name="stoichiometry">
                      <data type="decimal"/>
                    </attribute>
                  </optional>
                  <interleave>
                    <zeroOrMore>
                      <ref name="mathml.math"/>
                    </zeroOrMore>
                    <ref name="common-nodes"/>
                  </interleave>
                </group>
                <interleave>
                  <!-- The role attribute must take one of 7 values (7.4.3.2) -->
                  <attribute name="role">
                    <choice>
                      <value>reactant</value>
                      <value>product</value>
                    </choice>
                  </attribute>
                  <optional>
                    <!--
                      Reactants and products must be described in the forward
                      direction (7.4.3.5).
                    -->
                    <attribute name="direction">
                      <value>forward</value>
                    </attribute>
                  </optional>
                  <choice>
                    <interleave>
                      <!--
                        This must refer to the name of a variable in the current
                        component (7.4.3.7).  It must be unique across all role
                        elements within the current component.
                        It can only occur if the role is "reactant" or "product"
                        (7.4.3.8).
                      -->
                      <attribute name="delta_variable">
                        <ref name="ident"/>
                      </attribute>
                      <!--
                        When a delta_variable attribute is present, there must
                        be either a stoichiometry attribute or at least one math
                        element (7.4.3.8).
                      -->
                      <choice>
                        <!--
                          Usually this will be an integer, but fractional values
                          are allowed (7.4.3.6).
                        -->
                        <attribute name="stoichiometry">
                          <data type="decimal"/>
                        </attribute>
                        <oneOrMore>
                          <ref name="mathml.math"/>
                        </oneOrMore>
                      </choice>
                    </interleave>
                    <group>
                      <optional>
                        <attribute name="stoichiometry">
                          <data type="decimal"/>
                        </attribute>
                      </optional>
                      <zeroOrMore>
                        <ref name="mathml.math"/>
                      </zeroOrMore>
                    </group>
                  </choice>
                  <ref name="common-nodes"/>
                </interleave>
              </choice>
            </element>
          </oneOrMore>
          <element name="cellml:role">
            <!--
              The role attribute must take one of 7 values (7.4.3.2).
              If the value is "rate" then the reference variable
              represents the reaction rate, and no other roles can be
              assigned to it.  Further, the delta_variable and
              stoichiometry attributes are disallowed (7.4.3.3).
            -->
            <attribute name="role">
              <value>rate</value>
            </attribute>
            <optional>
              <!-- Rates must be specified in the forward direction (7.4.3.5) -->
              <attribute name="direction">
                <value>forward</value>
              </attribute>
            </optional>
            <interleave>
              <zeroOrMore>
                <ref name="mathml.math"/>
              </zeroOrMore>
              <ref name="common-nodes"/>
            </interleave>
          </element>
        </choice>
        <ref name="common-nodes"/>
      </interleave>
    </element>
  </define>
  <!--
    Almost any of MathML 2.0 is permitted.
    There is however a CellML subset,
    which is all that is required of conformant processing software.
  -->
  <!--
    This part uses a schema generated from the MathML 2.0 DTD to
    define the contents of math elements.
  -->
  <include href="../catalog/rng/mathml2.rng">
    <a:documentation/>
    <!--            Mathematics (section 4 of the specification)            # -->
    <a:documentation/>
    <!--
      Restrict the attribute list for math elements, since in a CellML
      document they're not top-level.
    -->
    <define name="attlist-mathml.math">
      <ref name="MATHML.Common.attrib"/>
    </define>
    <!--
      Presentation markup is NOT allowed except within annotation-xml.
      However, that element may contain any XML, so we can just define
      the presentation elements to not exist :)
    -->
    <define name="PresInCont">
      <empty/>
    </define>
    <!-- We don't want to allow empty expressions -->
    <define name="ContentExpression">
      <oneOrMore>
        <ref name="Content"/>
      </oneOrMore>
    </define>
    <!-- Restrict what is allowable "any XML" so ID attrs don't conflict -->
    <define name="any">
      <zeroOrMore>
        <choice>
          <element>
            <nsName ns="http://www.w3.org/1998/Math/MathML"/>
            <zeroOrMore>
              <attribute>
                <nsName ns="http://www.w3.org/1998/Math/MathML"/>
              </attribute>
            </zeroOrMore>
            <ref name="any"/>
          </element>
          <text/>
        </choice>
      </zeroOrMore>
    </define>
    <!--
      We could restrict the content of ci to be a CellML identifier:
      mathml.ci = element mathml:ci {
        attlist-mathml.ci, ident
      }
      However, since later it will be checked that each ci element contains
      the name of an existing variable, there isn't much point.
    -->
    <!-- Check numbers of operands using co-occurrence constraints -->
    <define name="mathml.apply">
      <element name="mathml:apply">
        <ref name="attlist-mathml.apply"/>
        <ref name="ApplyContentExpression"/>
      </element>
    </define>
    <!--
      I think some operators are wrongly classified in the MathML schema
      Lets be more specific about the 'misc' operators
    -->
    <define name="copmisc">
      <empty/>
    </define>
  </include>
  <!-- Extra unary operators that were misc. -->
  <define name="cop1ary" combine="choice">
    <choice>
      <ref name="mathml.root"/>
      <ref name="mathml.log"/>
      <ref name="mathml.minus"/>
      <ref name="cseqop"/>
      <ref name="cstatopmoment"/>
      <ref name="clogicopquant"/>
    </choice>
  </define>
  <!-- Be more specific for calculus operators -->
  <define name="ccalcop1ary" combine="choice">
    <choice>
      <ref name="mathml.int"/>
      <ref name="mathml.diff"/>
      <ref name="mathml.partialdiff"/>
      <ref name="mathml.divergence"/>
      <ref name="mathml.grad"/>
      <ref name="mathml.curl"/>
      <ref name="mathml.laplacian"/>
    </choice>
  </define>
  <define name="ccalcop2ary">
    <ref name="mathml.partialdiff"/>
  </define>
  <!-- Extra binary operators that were misc. -->
  <define name="cop2ary" combine="choice">
    <choice>
      <ref name="ccalcop2ary"/>
      <ref name="mathml.minus"/>
    </choice>
  </define>
  <!-- Restrict number of operands depending on the operator -->
  <define name="c_operand">
    <choice>
      <ref name="ctoken"/>
      <ref name="c0ary"/>
      <ref name="cconstructor"/>
      <ref name="cspecial"/>
      <ref name="cother"/>
    </choice>
  </define>
  <define name="c_not_oper">
    <choice>
      <ref name="cquantifier"/>
      <ref name="csemantics"/>
    </choice>
  </define>
  <define name="ApplyContentExpression">
    <choice>
      <interleave>
        <group>
          <ref name="cop1ary"/>
          <ref name="c_operand"/>
        </group>
        <zeroOrMore>
          <ref name="c_not_oper"/>
        </zeroOrMore>
      </interleave>
      <interleave>
        <group>
          <choice>
            <ref name="crel2ary"/>
            <ref name="cop2ary"/>
          </choice>
          <ref name="c_operand"/>
          <ref name="c_operand"/>
        </group>
        <zeroOrMore>
          <ref name="c_not_oper"/>
        </zeroOrMore>
      </interleave>
      <interleave>
        <group>
          <choice>
            <ref name="crelnary"/>
            <ref name="copnary"/>
          </choice>
          <oneOrMore>
            <ref name="c_operand"/>
          </oneOrMore>
        </group>
        <zeroOrMore>
          <ref name="c_not_oper"/>
        </zeroOrMore>
      </interleave>
    </choice>
  </define>
  <!-- All cn elements must contain a cellml:units attribute -->
  <define name="attlist-mathml.cn" combine="interleave">
    <attribute name="cellml:units">
      <ref name="ident"/>
    </attribute>
  </define>
  <!-- Allow binding time & lookup table annotations -->
  <define name="MATHML.Common.attrib" combine="interleave">
    <zeroOrMore>
      <attribute>
        <choice>
          <nsName ns="https://chaste.ediamond.ox.ac.uk/cellml/ns/partial-evaluation"/>
          <nsName ns="https://chaste.ediamond.ox.ac.uk/cellml/ns/lookup-tables"/>
        </choice>
      </attribute>
    </zeroOrMore>
  </define>
  <!-- This Schema doesn't say anything about allowable metadata. -->
  <define name="rdf-any">
    <a:documentation/>
    <!--                              Metadata                              # -->
    <a:documentation/>
    <choice>
      <element>
        <anyName>
          <except>
            <nsName ns="http://www.w3.org/1998/Math/MathML"/>
            <nsName ns="http://www.cellml.org/cellml/1.0#"/>
          </except>
        </anyName>
        <zeroOrMore>
          <attribute>
            <anyName/>
          </attribute>
        </zeroOrMore>
        <zeroOrMore>
          <ref name="rdf-any"/>
        </zeroOrMore>
      </element>
      <text/>
    </choice>
  </define>
  <define name="rdf.RDF">
    <element name="rdf:RDF">
      <zeroOrMore>
        <attribute>
          <anyName/>
        </attribute>
      </zeroOrMore>
      <zeroOrMore>
        <ref name="rdf-any"/>
      </zeroOrMore>
    </element>
  </define>
</grammar>