13. A system of one or more computers configured to perform operations comprising: identifying classified public content stored on a server appliance or a repository that is communicably coupled to the server appliance; identifying private content of a user stored on a client appliance or a repository that is communicably coupled to the client appliance, the client appliance communicably coupled to the server appliance through a network; receiving, from the user, i) a request for a recommendation of content and ii) a selection of a level of a hierarchical structure associated with the request for the recommendation of content; based on the selected level, determining one or more proxy keywords associated with one or more keywords of the request; generating a representative query based on i) the one or more proxy keywords and ii) the request for the recommendation of content; determining, based on the representative query, a portion of the classified public content stored on a server appliance or the repository that is communicably coupled to the server appliance; determining, based on the request, a portion of the private content stored on the client appliance or the repository that is communicably coupled to the client appliance; and preparing, for presentation to the user, the portion of the classified public content based on the representative query and the portion of the private content based on the request for the recommendation of content.
16. The system of claim 13 , wherein at least one of the client appliance, the server appliance, or the network comprises a firewall that restricts unauthorized access between the client appliance and the server appliance.