David Pidsley, The Decision Strategist at Gartner wrote: By “open” we’re referring to an open systems computing design pattern that allows for easy integration with other tools and platforms, often through well-documented APIs and standard protocols. Open systems provide some combination of interoperability, portability, and open software standards. This may but isn’t necessarily open source (with permission to use, copy and distribute it, either as is or with modifications, and that may be offered either free or with a charge – i.e. where the source code must be made available). Link