package org.lsst.ccs.command.annotations;
   
   import java.lang.annotation.Documented;
   import java.lang.annotation.ElementType;
   import java.lang.annotation.Retention;
   import java.lang.annotation.RetentionPolicy;
   import java.lang.annotation.Target;
   
   /**
   * Annotation for parameters of Command-marked methods. 
   */
  @Target(ElementType.PARAMETER)
  @Retention(RetentionPolicy.RUNTIME)
  @Documented
  public @interface Argument {
  
      public static final String NULL = "***NULL_VALUE_FOR_COMMAND_ARGUMENT***";
      
      /**
       * Optional parameter name. If not set the argument name will be "arg0",
       * "arg1"....
       *
       * @return The name of the argument.
       */
      String name();
  
      /**
       * One-sentence description of the parameter.
       *
       * @return Short description of the annotated argument.
       */
      String description() default "";
  
      /**
       * Default value for this Argument.
       *
       * @return the default value for this Argument.
       */
      String defaultValue() default NULL;
  }