recipe-xml/schema.xsd

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:element name="recipe">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="meta" type="MetaType" />
        <xs:element name="nutrition" type="NutritionType" />
        <xs:element name="ingredients" type="IngredientsType" />
        <xs:element name="steps" type="StepsType" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="StepsType">
    <xs:sequence>
      <xs:element name="step" type="StepType" minOccurs="1" maxOccurs="unbounded" />
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="MetaType">
    <xs:sequence>
      <xs:element name="categories" type="CategoriesType" minOccurs="0" maxOccurs="1" />
      <xs:element name="title" type="xs:string" />
      <xs:element name="author" type="xs:string" />
      <xs:element name="date" minOccurs="0" maxOccurs="1" type="xs:date" />
      <xs:element name="collections" minOccurs="0" maxOccurs="1" type="CollectionsType" />
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="NutritionType">
    <xs:sequence>
      <xs:element name="servings" type="xs:positiveInteger" />
      <xs:element name="servingSize" type="xs:string" />
      <xs:element name="caloriesPerServing" type="xs:positiveInteger" />
      <xs:element name="fat" type="xs:positiveInteger" />
      <xs:element name="cholesterol" type="xs:positiveInteger" />
      <xs:element name="sodium" type="xs:positiveInteger" />
      <xs:element name="fiber" type="xs:positiveInteger" />
      <xs:element name="sugars" type="xs:positiveInteger" />
      <xs:element name="totalCarbs" type="xs:positiveInteger" />
      <xs:element name="protein" type="xs:positiveInteger" />
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="CollectionsType">
    <xs:sequence>
      <xs:element name="collection" minOccurs="0" maxOccurs="unbounded" type="xs:string" />
    </xs:sequence>
  </xs:complexType>
  
  <xs:complexType name="CategoriesType">
    <xs:sequence>
      <xs:element name="category" minOccurs="0" maxOccurs="unbounded" type="xs:string" />
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="IngredientCategoryType">
    <xs:simpleContent>
      <xs:extension base="xs:string">
        <xs:attribute name="ref" type="xs:string" />
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
  
  <xs:complexType name="IngredientCategoriesType">
    <xs:sequence>
      <xs:element name="category" minOccurs="0" maxOccurs="unbounded" type="IngredientCategoryType" />
    </xs:sequence>
  </xs:complexType>
  
  <xs:complexType name="IngredientsType">
    <xs:sequence>
      <xs:element name="categories" type="IngredientCategoriesType" />
      <xs:element name="ingredient" type="IngredientType" minOccurs="1" maxOccurs="unbounded" />
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="IngredientType">
    <xs:attribute name="ref" type="xs:string" />
    <xs:attribute name="ingredient" type="xs:string" />
    <xs:attribute name="amount" type="xs:positiveInteger" />
    <xs:attribute name="unit" type="xs:string" />
    <xs:attribute name="categories" type="xs:string" />
  </xs:complexType>

  <xs:complexType name="StepType" mixed="true">
    <xs:sequence>
      <xs:element name="ingredient" minOccurs="0" maxOccurs="unbounded">
        <xs:complexType>
          <xs:attribute name="ref" type="xs:string" />
          <xs:attribute name="category" type="xs:string" />
        </xs:complexType>
      </xs:element>
    </xs:sequence>
    <xs:attribute name="ref" type="xs:string" />
    <xs:attribute name="sequence" type="xs:positiveInteger" />
  </xs:complexType>

</xs:schema>