Towards An Ontology Of Software: A Requirements Engineering Perspective / quote 17 of 28
Software systems versus software products
While the essential function of a software system is to control the external behavior of a certain machine (i.e., according to the Jackson et al.’s approach, that part of the behavior that is “visible” to both the environment and machine), the essential function of a software product is to control the environment’s behavior which is not visible to the machine, but can be influenced by it, under given environment (domain) assumptions, as a result of the interaction with the environment.