How to fetch X random entities of a given type using rules? I have a custom content type "project" with several CCK fields. One of them is named "field_old_intranet_url". No i want to assign a (random) user to every node of type "project". The author field or any other user_reference would be fine.

My first thought was to create a rule which is triggered when a user logs in. Fetch X random "projects" without an author and save the current user as the nodes author.

The problem is, that you can either fetch nodes by id or property. nid is not working, since i dont know the id. When fetching by property one can only compare the property with data from the current user or the current page. In my opinion it is not possible to fetch X random nodes.

Another solution would be, to trigger the rule by content creation or when content ist saved or whatever and then assign a random user. But this isnt possible either, because you cant fetch X user without a property to compare.

I hope my problem is clear and you can come up with quite different solutions!

Edit: It is possible to fetch every possible combination of X nodes of whatever type with Views Bulk Operations. This part of the problem is solved. Now the remaining challenge is to assign one entity of one of the lists (users / nodes) to a random one from the other, is this possible?

One solution would be to fetch a random node using views, is this possible?
Investigate the Views Module.  It can create lists of nodes for you.  Investigate node_load() and node_save().  They will allow you to modify those nodes.