* Supported values include "4.0.0" and "4.1.0".
     *
     * @return an {@link Optional} containing the model version, or empty if not specified
     */
    @Nonnull
    Optional<String> modelVersion();

    /**
     * Returns the directory to use as starting point for POM discovery.
     * If not specified, the current directory will be used.
     *

    <class rootElement="true" xml.tagName="metadata" java.clone="deep">
      <name>Metadata</name>
      <version>1.0.0+</version>
      <fields>
        <field xml.attribute="true" xml.tagName="modelVersion">
          <name>modelVersion</name>
          <version>1.1.0+</version>
          <type>String</type>
          <description>The version of the underlying metadata model.</description>
        </field>
        <field>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>com.google.guava</groupId>
    <artifactId>guava-parent</artifactId>
    <version>999.0.0-HEAD-jre-SNAPSHOT</version>
  </parent>
  <artifactId>guava-gwt</artifactId>

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <groupId>com.google.guava</groupId>
  <artifactId>guava-parent</artifactId>
  <version>999.0.0-HEAD-android-SNAPSHOT</version>
  <packaging>pom</packaging>
  <name>Guava Maven Parent</name>

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>
  <groupId>com.google.guava</groupId>
  <artifactId>guava-parent</artifactId>
  <version>999.0.0-HEAD-jre-SNAPSHOT</version>
  <packaging>pom</packaging>
  <name>Guava Maven Parent</name>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<artifactId>fess</artifactId>
	<version>15.2.1-SNAPSHOT</version>
	<packaging>war</packaging>
	<name>Fess</name>
	<description>Fess is Full tExt Search System.</description>
	<url>https://fess.codelibs.org/</url>

        <!-- Model Version                                                          -->
        <!-- ====================================================================== -->

        <field>
          <name>modelVersion</name>
          <version>4.0.0+</version>
          <required>true</required>
          <description>Declares to which version of project descriptor this POM conforms.</description>
          <type>String</type>