String version,
            String message) {
        this.artifact = Objects.requireNonNull(artifact, "artifact cannot be null");
        this.groupId = (groupId != null && !groupId.isEmpty()) ? groupId : null;
        this.artifactId = (artifactId != null && !artifactId.isEmpty()) ? artifactId : null;
        this.classifier = (classifier != null && !classifier.isEmpty()) ? classifier : null;

  <groupId>maven-test</groupId>
  <artifactId>maven-test-b</artifactId>
  <packaging>jar</packaging>
  <version>1.0</version>
  <dependencies>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>maven-test-c</artifactId>
      <version>1.0</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>maven-test</groupId>

  <groupId>maven-test</groupId>
  <artifactId>t05-b</artifactId>
  <packaging>jar</packaging>
  <version>1.1</version>
  <dependencies>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t05-c</artifactId>
      <version>1.0</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>maven-test</groupId>

			<version>2.0.16</version>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>commons-logging</groupId>
			<artifactId>commons-logging</artifactId>
			<version>1.3.5</version>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.13.2</version>
			<scope>test</scope>
		</dependency>
	</dependencies>

  <groupId>maven-test</groupId>
  <artifactId>t05-b</artifactId>
  <packaging>jar</packaging>
  <version>2.0</version>
  <dependencies>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t05-c</artifactId>
      <version>1.0</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>maven-test</groupId>

  <groupId>maven-test</groupId>
  <artifactId>t08-b</artifactId>
  <packaging>jar</packaging>
  <version>1.0</version>
  <dependencies>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t08-c</artifactId>
      <version>1.0</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>maven-test</groupId>

    <artifactId>p0</artifactId>
    <groupId>maven-t09</groupId>
    <version>1.0</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>
  <groupId>maven-t09</groupId>
  <artifactId>p1</artifactId>
  <packaging>pom</packaging>
  <name>p1</name>
  <version>1.0</version>
  <scm>
    <url>scm-url</url>
  </scm>

  <dependencies>

    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t09-a</artifactId>

                    <modelVersion>4.0.0</modelVersion>
                    <groupId>test</groupId>
                    <artifactId>test</artifactId>
                    <version>1.0.0</version>
                    <build>
                        <plugins>
                            <plugin>
                                <groupId>org.apache.maven.plugins</groupId>
                                <artifactId>maven-compiler-plugin</artifactId>

 Depending on what the directory represents ("groupId", "groupId/artifactId" or "groupId/artifactId/version"),
 the Maven Repository Metadata file contains 3 different sets of metadata:

 [[1]] in a "groupId" directory: a "groupId" directory may contain Maven plugins artifacts, which are described in metadata's <<<plugins>>> element,

 [[2]] in a "groupId/artifactId" directory: metadata describes <<<groupId>>>, <<<artifactId>>> and <<<versioning>>> element that

-->

<project>
  <modelVersion>4.0.0</modelVersion>
  <artifactId>aid</artifactId>
  <groupId>gid</groupId>
  <version>0.1</version>

  <build>
    <plugins>
      <plugin>
        <groupId>test</groupId>
        <artifactId>good</artifactId>
        <version>1.0</version>
      </plugin>
      <plugin>
        <groupId>test</groupId>
        <artifactId>mip</artifactId>
        <version>${missing.property}</version>