1. A method comprising: performing, by a processor, semantic/syntactic analysis for sentences of a text document to construct semantic-syntactic structures for the sentences; applying, by the processor, production rules to the semantic-syntactic structures to generate a set of logical conclusions about information objects in the text document, wherein the production rules are based on linguistic characteristics of the semantic-syntactic structures, lexical-morphological properties of the semantic-syntactic structures, and ontologies of subject matters for the sentences, wherein the production rules comprise interpretation rules and identification rules, wherein the interpretation rules specify fragments to be found in the semantic-syntactic structures, wherein the interpretation rules specify corresponding logical statements that form the set of logical conclusions in response to finding the fragments in the semantic-syntactic structures, and wherein the identification rules are used to merge ones of the information objects; using, by the processor, the set of logical conclusions about the information objects in the text document to build an ontology-based Resource Definition Framework (RDF) graph; and storing the ontology-based RDF graph in a storage device and providing searching of the stored ontology-based RDF graph as a knowledge base reference.