Interoperability (of the web and the internet) = the ability to use and combine many different form of media, using a single platform
"Interoperability: The ability of a User to technically execute Functions through Interfaces and Protocols, based on open specifications, with predictable results" (http://camorra.org/swann/2007/07/11/daniels-drm-dilemma/)
Lawrence Lessig: "Perhaps the most important thing that the Internet has given us is a platform upon which experience is interoperable. At first, the aim of the computer and network geniuses was simply to find a way to make computers talk to each other. Then application geniuses found ways to make the content that runs on these different devices interoperate on a single digital platform. We are close to a world where any format of sound can be mixed with any format of video, and then supplemented with any format of text or images. There are exceptions; there are some who don't play in this interoperability game. But the push of the network has been to produce a world where anyone can clip and combine just about anything to make something new. Just as the senses process many different kinds of experiences (sound, images, smell, emotions) and then offer them for translation on a single platform (the brain), so too have digital networks made it possible to combine many forms of media, and make them usable on single platform." (http://creativecommons.org/weblog/entry/5676)
Bruno Perens in the Sincere Choice policy platform, calls for choice through interoperability:
"No user should be required to use a particular product simply because other users do. Competing products should interoperate with each other through Open Standards.
There is a place for standardization: the part of a program that communicates with other computers through file exchange and networking. And there is a place for product differentiation: everywhere else. If file formats and intercommunication formats are standardized, competing products will be able to interoperate. This will help create a healthy software ecosystem in which competitors win, or lose, based on the merit of their programs, rather than the degree to which they have locked in their users. Economics will drive down the cost of software and drive improvements in quality." (http://www.sincerechoice.org/Principles/Choice_Through_Interoperability.html)