1. A method comprising: accessing a topological database with multi-tenancy capability that represents an information technology environment, each node of the topological database representing a configuration item within the environment, each node being characterized by a tenant authorization rule (TAR) that indicates a list of tenants of the topological database that are authorized to access the configuration item that corresponds to that node; obtaining an unrestricted result to an unrestricted query, the unrestricted query being representable as a sub-graph isomorphism, the unrestricted result to the unrestricted query including any groups of the nodes of the database that satisfy the sub-graph isomorphism; applying a tenant query to the unrestricted result to obtain an authorized result, the tenant query being representable by a sub-graph isomorphism that is substantially of the same form as the sub-graph isomorphism representation of the unrestricted query, the authorized result including identification of any of the groups whose component nodes are each characterized by a TAR that authorizes access by the querying tenant; and issuing a notification on the basis of the obtained authorized result.