;-------------------------------- keywords ------------------------------------
<pregutas_keywords> ->
   (what | which) <pregunta_place> | 
   <pregunta_theme>
)
<cont_preguntas_keywords> ->
   <cont_pregunta_theme>
)
<infs_keywords> ->
   <inf_place> | <inf_theme>
)
<pregunta_place> -> (
   ?geographic area does map cover
)
<inf_place> -> (
   ?((of | for) (?all ?the) maps) 
      (of | in | which place is | related to) <nombre_propio_place>
) 
<pregunta_theme> -> (
   (what | which) (
      is <cont_pregunta_theme> | 
      <cont_pregunta_theme> (does maps cover | are covered ?(by maps))) |
   ?all ?the themes
)
<cont_pregunta_theme> -> (
   ?the theme ?(of information)
) 
<inf_theme> -> (
   (of | which theme is | with the theme) <nombre_propio_theme>
) 
<atributos_inf_keywords> -> (
   stratum | theme 
)
<atributos_pregunta_keywords> -> (
   stratum | (place | ?the ?geographic area ?covered)
)  


<nombre_propio_place> -> (Aragon | Zaragoza | Huesca | Teruel | China | India | Canada)
<nombre_propio_theme> -> (politica | exportaciones | inmigracion)