The initial problem was always the same, the site, in php, had no keywords at all in the text and client would not modify it.
To overcome it I've created a link <link rel="Glossario" href="yyyyyyy.html" type="text/html"> in the <HEAD> towards a page with the right txt in it.
I've hidden the yyyyyyy.html with mod_rewrite [R] and created a server side redir
(error 404) to a site_map.html (for users).
I've controlled the behaviour of the spiders and found that they arrive to the site_map.html too but have not seen the
crawling of the linked page (yyyyyyy.html).
What d'you think about that?
Hope to have been clear enough.
Many thank for your advice.