I read the Facebook developers guide, but I'm not sure to have well understood wheter my goal is achievable or not. I have developed a small app that asks to users their topics of interest, so they will receive filtered updates on those topics. This currently works, my database stores users and topics. Now I want to publish on registered users stream a newsfeed if there are updates on the topics they selected (in the oauth dialog I asked permissions for "publish_actions"). My app doesn't use OpenGraph, I would that the newsfeed has my apps as title, a small picture and a brief description and it links to and external site (not mine). The feed is personalized, so that's why I don't use a Facebook page.
Is it possible to realize this? Thanks in advance
This is not allowed by Facebook Platform Policies. Publishing something to the wall must be related to something the user has done, e.g. User has read an article or User has achieved a high score. Posting an link / article to the user's wall is not allowed since it's not a direct action the user has taken.
Instead, you should provide the user with personalised RSS feeds. Each user would have their own RSS feed related to the topics they have indicated they are interested in. Facebook shouldn't be used in this way.