PMML通过XML表示模型，模型的结构以XML Schema描述。在一个PMML文档中，可以包含一个或多个模型。PMML文档结构如下：

<?xml version="1.0"?>
<PMML version="4.3"
  xmlns="http://www.dmg.org/PMML-4_3" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <Header copyright="Example.com"/>
  <DataDictionary> ... </DataDictionary>

  ... a model ...

</PMML>

PMML Schema的namespace定义在

  <xs:schema
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.dmg.org/PMML-4_3"
    xmlns="http://www.dmg.org/PMML-4_3"
    elementFormDefault="unqualified">

PMML文档的root元素必须包含PMML类型

<xs:element name="PMML">
  <xs:complexType>
    <xs:sequence>
      <xs:element ref="Header"/>
      <xs:element ref="MiningBuildTask" minOccurs="0"/>
      <xs:element ref="DataDictionary"/>
      <xs:element ref="TransformationDictionary" minOccurs="0"/>
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
        <xs:group ref="MODEL-ELEMENT"/>
      </xs:sequence>
      <xs:element ref="Extension" minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:attribute name="version" type="xs:string" use="required"/>
  </xs:complexType>
</xs:element>

<xs:group name="MODEL-ELEMENT">
  <xs:choice>
    <xs:element ref="AssociationModel"/>
    <xs:element ref="BayesianNetworkModel"/>
    <xs:element ref="BaselineModel"/>
    <xs:element ref="ClusteringModel"/>
    <xs:element ref="GaussianProcessModel"/>
    <xs:element ref="GeneralRegressionModel"/>
    <xs:element ref="MiningModel"/>
    <xs:element ref="NaiveBayesModel"/>
    <xs:element ref="NearestNeighborModel"/>
    <xs:element ref="NeuralNetwork"/>
    <xs:element ref="RegressionModel"/>
    <xs:element ref="RuleSetModel"/>
    <xs:element ref="SequenceModel"/>
    <xs:element ref="Scorecard"/>
    <xs:element ref="SupportVectorMachineModel"/>
    <xs:element ref="TextModel"/>
    <xs:element ref="TimeSeriesModel"/>
    <xs:element ref="TreeModel"/>
  </xs:choice>
</xs:group>