Kinds of Systems (Ludwig Von Bertalanffy,1972)
Real System (concrete, or physical) which entities are perceived in or inferred from observation and existing independently of an observer; they can be man-made or natural, living or non-living systems
Conceptual Systems which essentially are symbolic idea constructs(linguistic, mathematics, logic);
Abstracted System which is conceptual systems corresponding with reality (model of traffic, a bridge)
Living and Organic Systems: see p37 specific qualities differentiate living systems from non-living ones (Structure & genetic; co-ordination &subordination, control &freedom; qualitatively transform &continuously renew).