1. A method comprising: configuring, by a computer system, a data structure according to an ontology, wherein the data structure configured according to the ontology comprise a plurality of concepts that are organized in hierarchical layers and that are linked by a set of relationships; generating, by the computer system, an index representing stored content based on the data structure configured according to the ontology; receiving, by the computer system, a query comprising a natural language expression or a natural language question; parsing, by the computer system, the query into elements; annotating, by the computer system, the elements so that each element has an associated annotation, wherein the associated annotation defines the respective element as one or both of conceptual and canonical based on the ontology; comparing, by the computer system, a first condition of one or more rules from a rules dictionary against the elements and the associated annotations; comparing, by the computer system, a second condition of the one or more rules from the rules dictionary against peripheral information attributed to a querier, wherein the peripheral information is distinct from the query and is retrieved from a peripheral information repository; generating, by the computer system, an action list corresponding to one or more actions of the one or more rules based on whether the first condition and the second condition are satisfied, the action list comprising first search operator criteria that specifies a first scoring scope of search and second search operator criteria that specifies a second scoring scope of search, wherein the first scoring scope of search is different from the second scoring scope of search in order of priority and scoring; selecting, by the computer system and based on one or both of the first search operator criteria and the second search operator criteria in the action list, one or more retrieval technologies from a plurality of retrieval technologies, the plurality of retrieval technologies comprising a keyword searching technology, a document-level relevance-based searching technology, and an ontology-based searching technology; performing, by the computer system, the one or more actions, the one or more actions comprising using the selected one or more retrieval technologies to retrieve stored content represented in the index based on the elements and the associated annotations; and generating, by the computer system, a response to the query using the stored content retrieved based on the index.