@Nullable
    InputStream getInputStream();

    @Nullable
    Reader getReader();

    @Nullable
    Transformer getTransformer();

    boolean isStrict();

    @Nullable
    String getModelId();

    @Nullable
    String getLocation();

    boolean isAddDefaultEntities();

    interface Transformer {
        /**
         * Interpolate the value read from the xml document
         *

    /**
     * Get the identifier of the POM in the format {@code
     * <groupId>:<artifactId>:<version>}.
     *
     * @return String
     */
    public String getModelId() {
        return this.modelId;
    } // -- String getModelId()

    /**
     * Set the path/URL of the POM or {@code null} if unknown.
     *
     * @param location
     */
    public void setLocation(String location) {

            if (req.getLocation().getSource() != null) {
                modelId = req.getLocation().getSource().getModelId();
                source = req.getLocation().getSource().getLocation();
            }
        }

        if (modelId == null) {
            modelId = getModelId();
            source = getSource();
        }

     * exception is thrown so this information is merely meant to assist the user.
     *
     * @return The identifier of the POM or an empty string if not known, never {@code null}.
     */
    public String getModelId() {
        if (result == null) {
            return "";
        } else if (result.getEffectiveModel() != null) {
            return result.getEffectiveModel().getId();
        } else if (result.getRawModel() != null) {

     *
     * @return The identifier of the model from which the problem originated or an empty string if unknown, never
     *         {@code null}.
     */
    @Nonnull
    String getModelId();

    /**
     * Gets the applicable maven version/validation level of this problem
     * @return The version, never {@code null}.
     */
    @Nonnull
    Version getVersion();

     *
     * @return the model identifier, or {@code null} if not available or not applicable
     * @since 4.0.0
     */
    @Nullable
    default String getModelId() {
        return null;
    }

    /**
     * Interface for locating POM files within a project structure.
     * Implementations of this interface provide the ability to find POM files

     * exception is thrown so this information is merely meant to assist the user.
     *
     * @return The identifier of the POM or an empty string if not known, never {@code null}.
     */
    public String getModelId() {
        if (result == null || result.getModelIds().isEmpty()) {
            return "";
        }
        return result.getModelIds().get(0);
    }

    /**

    public int getLineNumber() {
        return lineNumber;
    }

    @Override
    public int getColumnNumber() {
        return columnNumber;
    }

    @Override
    public String getModelId() {
        return modelId;
    }

    @Override
    public Exception getException() {
        return exception;
    }

    @Override
    public String getMessage() {
        String msg;

     *
     * @return The identifier of the model from which the problem originated or an empty string if unknown, never
     *         {@code null}.
     */
    String getModelId();

    /**
     * Gets the exception that caused this problem (if any).
     *
     * @return The exception that caused this problem or {@code null} if not applicable.
     */
    Exception getException();

            this.modelId = modelId;
        }

        @Override
        public Path getPath() {
            return null;
        }

        @Override
        @Nullable
        public String getModelId() {
            return modelId;
        }

        @Override
        public Source resolve(String relative) {
            return null;
        }

        @Override
        @Nullable