Concepts, data, objectives, requirements, rules, and specifications as an organized knowledge repository. Typically this is a computer system, less often, an organization. It can be (1) a retrieval either as an expert system or artificial intelligence; (2) a human-based retrieval. As a system, it is software-based relational using data forms, design constructs, couplings, and linkages. As a human, physical documents and textual information is its basis.