A system and method provide for querying a knowledge base. The knowledge base includes a plurality of layers, each layer corresponding to a different type of information, such as user's intent, lack of knowledge, and specific issue. The system includes categorization rules for categorizing at least a part of a user's request according to the types of information and for mapping the request to respective layers of the knowledge base. The user's request is categorized with the categorization rules and mapped to one of the layers of the knowledge base, based on the categorization. A search is conducted for responsive problem descriptions among the problem descriptions in that layer. The system and method can thus provide for differential searching of the knowledge base, depending on the type of information being sought.