}
            }
            return null;
        }
    }

    /**
     * Ensures that expressions referring to URLs evaluate to normalized URLs.
     *
     */
    static class UrlNormalizingPostProcessor implements InterpolationPostProcessor {

        private static final Set<String> URL_EXPRESSIONS;

          <description>
            <![CDATA[
            The classifier of the dependency. It is appended to
            the filename after the version. This allows:
            <ul>
            <li>referring to attached artifact, for example {@code sources} and {@code javadoc}:
            see <a href="../maven-core/artifact-handlers.html">default artifact handlers</a> for a list,</li>
            <li>distinguishing two artifacts