// Properties

    /**
     * Sets the system properties to use for interpolation and profile activation. The system properties are collected
     * from the runtime environment like {@link System#getProperties()} and environment variables.
     *
     * @param systemProperties The system properties, may be {@code null}.
     * @return This request, never {@code null}.
     */

     *
     * @return The system properties, never {@code null}.
     */
    Properties getSystemProperties();

    /**
     * Sets the system properties to use for interpolation and profile activation. The system properties are collected
     * from the runtime environment like {@link System#getProperties()} and environment variables.
     *

            final Model model, final File projectDir, final ProjectBuilderConfiguration config) {
        String timestampFormat = DEFAULT_BUILD_TIMESTAMP_FORMAT;

        Properties modelProperties = model.getProperties();
        if (modelProperties != null) {
            timestampFormat = modelProperties.getProperty(BUILD_TIMESTAMP_FORMAT_PROPERTY, timestampFormat);
        }

        Activation defaultActivation = new Activation();

        defaultActivation.setActiveByDefault(true);

        defaultActivated.setActivation(defaultActivation);

        Properties props = System.getProperties();

        ProfileManager profileManager = new DefaultProfileManager(getContainer(), props);

        profileManager.addProfile(notActivated);
        profileManager.addProfile(defaultActivated);

            if (sourceDominant) {
                merged.putAll(target.getProperties());
                putAll(merged, source.getProperties(), CHILD_DIRECTORY_PROPERTY);
            } else {
                putAll(merged, source.getProperties(), CHILD_DIRECTORY_PROPERTY);
                merged.putAll(target.getProperties());
            }
            builder.properties(merged);
            builder.location(

        Properties properties = getMavenProject(project).getProperties();
        if (value == null) {
            properties.remove(key);
        } else {
            properties.setProperty(key, value);
        }
    }

    @Override
    public Map<String, String> getProperties(Project project) {
        return Collections.unmodifiableMap(

    }

    /**
     * Gets the system properties to use for interpolation and profile activation. The system properties are collected
     * from the runtime environment like {@link System#getProperties()} and environment variables.
     *
     * @return The system properties, never {@code null}.
     */
    public Properties getSystemProperties() {
        return request.getSystemProperties();
    }

        return systemProperties;
    }

    /**
     * Sets the system properties to use for interpolation and profile activation. The system properties are collected
     * from the runtime environment like {@link System#getProperties()} and environment variables.
     *
     * @param systemProperties The system properties, may be {@code null}.
     * @return This context, never {@code null}.
     */
    @SuppressWarnings("unchecked")

     * environment like {@link System#getProperties()} and environment variables.
     *
     * @return The system properties, never {@code null}.
     */
    Properties getSystemProperties();

    /**
     * Sets the system properties to use for interpolation. The system properties are collected from the runtime
     * environment like {@link System#getProperties()} and environment variables.
     *

        projectReferences.put(
                getProjectReferenceId(project.getGroupId(), project.getArtifactId(), project.getVersion()), project);
    }

    public Properties getProperties() {
        return getModel().getProperties();
    }

    public List<String> getFilters() {
        return getBuild().getFilters();
    }

    public Map<String, MavenProject> getProjectReferences() {