</description>
          <type>String</type>
        </field>
        <field>
          <name>checksumPolicy</name>
          <version>1.0.0+</version>
          <description>
            What to do when verification of an artifact checksum fails. Valid values are "fail" (default for Maven 4 and
            above), "warn" (default for Maven 2 and 3) or "ignore".
          </description>
          <type>String</type>

        // effective model.
        //
        // As of 3.4, the model version is mandatory even in raw models. The XML element still is optional in the
        // XML schema and this will not change anytime soon. We do not want to build effective models based on
        // models without a version starting with 3.4.
        validateStringNotEmpty("modelVersion", problems, Severity.ERROR, Version.V20, m.getModelVersion(), m);

        return Arrays.asList(A, B, C, X, Y, Z, UNKNOWN);
    }

    public List<MavenProject> getSortedProjects() {
        return Arrays.asList(A, B, C, X, Y, Z); // I'm not entirely sure about the order but this should do...
    }

    public List<MavenProject> getDownstreamProjects(MavenProject project, boolean transitive) {
        if (transitive) {
            throw new RuntimeException("Not implemented yet");
        }

        if (entry == null) {
            return null;
        }

        if (graph.isEmpty()) {
            throw new GraphConflictResolutionException("graph with an entry, but not vertices do not exist");
        }

        if (graph.isEmptyEdges()) {
            return null; // no edges - nothing to worry about
        }

        final TreeSet<MetadataGraphVertex> vertices = graph.getVertices();

additions to the Program originate from and are distributed by that particular Contributor. A Contribution 'originates' from a Contributor if it was added to the Program by such Contributor itself or anyone acting on such Contributor's behalf. Contributions do not include additions to the Program which: (i) are separate modules of software distributed in conjunction with the Program under their own license agreement, and (ii) are not derivative works of the Program. "Contributor" means any person or entity...