* <p><b>Algorithm:</b>
     * If the given path is a directory, then there is a choice:
     * </p>
     * <ul>
     *   <li><b>Package hierarchy:</b> if a {@code module-info.class} file is found at the root,
     *       then builds a singleton map with the module name declared in that descriptor.</li>
     *   <li><b>Module hierarchy:</b> if {@code module-info.class} files are found in sub-directories,

 *     <li><code>alpha</code> or <code>a</code></li>
 *     <li><code>beta</code> or <code>b</code></li>
 *     <li><code>milestone</code> or <code>m</code></li>
 *     <li><code>rc</code> or <code>cr</code></li>
 *     <li><code>snapshot</code></li>
 *     <li><code>(the empty string)</code> or <code>ga</code> or <code>final</code></li>
 *     <li><code>sp</code></li>
 *     </ul>

     * <ul>
     *   <li>If it starts with either "pom." or "project.", the expression is evaluated against the model.</li>
     *   <li>If the value is null, get the value from the context.</li>
     *   <li>If the value is null, but the context contains the expression, don't replace the expression string
     *       with the value, and continue to find other expressions.</li>

/**
 * Specific problems during resolution that we want to account for:
 * <ul>
 *   <li>missing metadata</li>
 *   <li>version range violations</li>
 *   <li>version circular dependencies</li>
 *   <li>missing artifacts</li>
 *   <li>network/transfer errors</li>
 *   <li>file system errors: permissions</li>
 * </ul>
 *
 * TODO carlos: all these possible has*Exceptions and get*Exceptions methods make the clients too

     * <ul>
     * <li>collect all the vertices for the projects that we want to build.</li>
     * <li>iterate through the deps of each project and if that dep is within
     * the set of projects we want to build then add an edge, otherwise throw
     * the edge away because that dependency is not within the set of projects
     * we are trying to build. we assume a closed set.</li>
     * <li>do a topo sort on the graph that remains.</li>

     * <ul>
     * <li>{@code *} = everything,</li>
     * <li>{@code external:*} = everything not on the localhost and not file based,</li>
     * <li>{@code external:http:*} = any repository not on the localhost using HTTP,</li>
     * <li>{@code repo,repo1} = {@code repo} or {@code repo1},</li>
     * <li>{@code *,!repo1} = everything except {@code repo1}.</li>
     * </ul>
     *

     * Some spec examples are:
     * <ul>
     * <li><code>1.0</code> Version 1.0 as a recommended version</li>
     * <li><code>[1.0]</code> Version 1.0 explicitly only</li>
     * <li><code>[1.0,2.0)</code> Versions 1.0 (included) to 2.0 (not included)</li>
     * <li><code>[1.0,2.0]</code> Versions 1.0 to 2.0 (both included)</li>
     * <li><code>[1.5,)</code> Versions 1.5 and higher</li>

     * defined precedence onto each other to achieve proper precedence. Precedence is defined as:
     * <ul>
     *     <li>System properties (lowest precedence)</li>
     *     <li>Project properties (optional)</li>
     *     <li>User properties (highest precedence)</li>
     * </ul>
     * Note: Project properties contains properties injected from profiles, if applicable. Their precedence is

            Type of toolchain:<ul>
            <li>{@code jdk} for <a
            href="https://maven.apache.org/plugins/maven-toolchains-plugin/toolchains/jdk.html">JDK Standard Toolchain</a>,</li>
            <li>other value for <a
            href="https://maven.apache.org/plugins/maven-toolchains-plugin/toolchains/custom.html">Custom Toolchain</a></li>
            </ul>
          </description>

    <p>An XSD is available at:</p>
    <ul>
      <li><a href="https://maven.apache.org/xsd/maven-v3_0_0.xsd">https://maven.apache.org/xsd/maven-v3_0_0.xsd</a> for Maven 1.1.</li>
      <li><a href="https://maven.apache.org/xsd/maven-4.0.0.xsd">https://maven.apache.org/xsd/maven-4.0.0.xsd</a> for Maven 2.0.</li>